diff --git a/internal/db/db.go b/internal/db/db.go
index 087debb..d9e9cac 100644
--- a/internal/db/db.go
+++ b/internal/db/db.go
@@ -178,6 +178,10 @@ func runMigrations(d *sql.DB) error {
 		// (separate from last_respec_at, which gates the full character wipe).
 		`ALTER TABLE dnd_character ADD COLUMN subclass TEXT NOT NULL DEFAULT ''`,
 		`ALTER TABLE dnd_character ADD COLUMN last_subclass_respec_at DATETIME`,
+		// Phase 10 SUB2a — exhaustion levels. Berserker Frenzy increments
+		// this after each rage'd combat. Cleared on long rest. Reused by
+		// other classes once exhaustion-inducing mechanics arrive in SUB3+.
+		`ALTER TABLE dnd_character ADD COLUMN exhaustion INTEGER NOT NULL DEFAULT 0`,
 	}
 	for _, stmt := range columnMigrations {
 		if _, err := d.Exec(stmt); err != nil {
diff --git a/internal/plugin/combat_bridge.go b/internal/plugin/combat_bridge.go
index ea0556d..e12a8f4 100644
--- a/internal/plugin/combat_bridge.go
+++ b/internal/plugin/combat_bridge.go
@@ -45,6 +45,7 @@ func (p *AdventurePlugin) runArenaCombat(
 	applyDnDHPScaling(&playerStats, dndChar)
 	applyClassPassives(&playerStats, &playerMods, dndChar)
 	applyRacePassives(&playerStats, &playerMods, dndChar)
+	applySubclassPassives(&playerStats, &playerMods, dndChar)
 	if firedName, fired := applyArmedAbility(dndChar, &playerMods); fired {
 		slog.Info("dnd: armed ability fired", "user", userID, "ability", firedName)
 	}
@@ -89,6 +90,9 @@ func (p *AdventurePlugin) runArenaCombat(
 	p.grantCombatAchievements(userID, result)
 
 	persistDnDHPAfterCombat(userID, result.PlayerStartHP, result.PlayerEndHP)
+	if err := persistDnDPostCombatSubclass(dndChar, playerMods.BerserkerRage); err != nil {
+		slog.Error("dnd: post-combat subclass persist (arena)", "user", userID, "err", err)
+	}
 
 	if xp := arenaCombatXP(result, monster.ThreatLevel); xp > 0 {
 		if _, err := p.grantDnDXP(userID, xp); err != nil {
@@ -169,6 +173,7 @@ func (p *AdventurePlugin) runDungeonCombat(
 	applyDnDHPScaling(&playerStats, dndChar)
 	applyClassPassives(&playerStats, &playerMods, dndChar)
 	applyRacePassives(&playerStats, &playerMods, dndChar)
+	applySubclassPassives(&playerStats, &playerMods, dndChar)
 	if firedName, fired := applyArmedAbility(dndChar, &playerMods); fired {
 		slog.Info("dnd: armed ability fired", "user", userID, "ability", firedName)
 	}
@@ -215,6 +220,9 @@ func (p *AdventurePlugin) runDungeonCombat(
 	p.grantCombatAchievements(userID, result)
 
 	persistDnDHPAfterCombat(userID, result.PlayerStartHP, result.PlayerEndHP)
+	if err := persistDnDPostCombatSubclass(dndChar, playerMods.BerserkerRage); err != nil {
+		slog.Error("dnd: post-combat subclass persist (dungeon)", "user", userID, "err", err)
+	}
 
 	if xp := dungeonCombatXP(result, loc.Tier); xp > 0 {
 		if _, err := p.grantDnDXP(userID, xp); err != nil {
diff --git a/internal/plugin/combat_engine.go b/internal/plugin/combat_engine.go
index 705b7d0..8c1945f 100644
--- a/internal/plugin/combat_engine.go
+++ b/internal/plugin/combat_engine.go
@@ -53,6 +53,21 @@ type CombatModifiers struct {
 	RageReady    bool // Orc: when HP first drops <50%, next attack deals +50% damage
 	PoisonResist bool // Dwarf: poison tick damage halved
 
+	// Phase 10 SUB2a — subclass combat hooks.
+	// CritThreshold: lowest d20 roll that crits. 0 = use default (20).
+	// Champion L5 Improved Critical sets this to 19; Champion L15
+	// Superior Critical (SUB3) will set 18.
+	CritThreshold int
+	// BerserkerRage: while true, +RageMeleeDmg flat damage per hit and
+	// incoming weapon damage halved (PhysicalResistRage). Frenzy also
+	// adds FrenzyDmgBonus on top to model the bonus-attack-per-turn that
+	// one-shot combat can't represent literally. Set by armed `rage`
+	// ability for Berserker subclass.
+	BerserkerRage      bool
+	RageMeleeDmg       int     // flat damage per hit while raging (5: +2)
+	PhysicalResistRage bool    // halve incoming physical damage while raging
+	FrenzyDmgBonus     float64 // multiplicative dmg bump while raging (Frenzy approximation)
+
 	// Phase 9 — pending spell resolution. Set by applyPendingCast in
 	// dnd_spell_combat.go before SimulateCombat runs. SpellPreDamage is
 	// dealt as a pre-combat event with SpellPreDamageDesc as the narrative
@@ -469,7 +484,13 @@ func resolvePlayerAttack(st *combatState, player, enemy *Combatant, phase *Comba
 		roll = newRoll
 	}
 	isFumble := roll == 1
-	isNat20 := roll == 20
+	// Phase 10 SUB2a — Champion Improved Critical lowers the crit floor.
+	// CritThreshold==0 means "use default" (nat 20). Champion sets 19.
+	critFloor := 20
+	if player.Mods.CritThreshold > 0 && player.Mods.CritThreshold < 20 {
+		critFloor = player.Mods.CritThreshold
+	}
+	isCritRoll := roll >= critFloor
 	// Class proficiency penalty (appendix §8): -4 attack with a non-proficient weapon.
 	attackBonus := player.Stats.AttackBonus
 	if player.Stats.Weapon != nil && !player.Stats.WeaponProficient {
@@ -477,7 +498,7 @@ func resolvePlayerAttack(st *combatState, player, enemy *Combatant, phase *Comba
 	}
 	total := roll + attackBonus
 
-	if isFumble || (!isNat20 && total < enemy.Stats.AC) {
+	if isFumble || (!isCritRoll && total < enemy.Stats.AC) {
 		desc := ""
 		if isFumble {
 			desc = "fumble"
@@ -518,7 +539,7 @@ func resolvePlayerAttack(st *combatState, player, enemy *Combatant, phase *Comba
 		dmg = max(1, dmg/2)
 	}
 
-	isCrit := isNat20
+	isCrit := isCritRoll
 	if st.autoCrit {
 		isCrit = true
 		st.autoCrit = false
@@ -533,6 +554,17 @@ func resolvePlayerAttack(st *combatState, player, enemy *Combatant, phase *Comba
 		dmg = int(float64(dmg) * 1.5)
 		st.pendingRageAttack = false
 	}
+	// Phase 10 SUB2a — Berserker rage: +flat per hit, plus Frenzy
+	// multiplicative bump that approximates the bonus-attack-per-turn we
+	// can't model in one-shot combat.
+	if player.Mods.BerserkerRage {
+		if player.Mods.RageMeleeDmg > 0 {
+			dmg += player.Mods.RageMeleeDmg
+		}
+		if player.Mods.FrenzyDmgBonus > 0 {
+			dmg = int(float64(dmg) * (1 + player.Mods.FrenzyDmgBonus))
+		}
+	}
 	dmg = max(1, dmg)
 
 	action := "hit"
@@ -620,6 +652,11 @@ func resolveEnemyAttack(st *combatState, player, enemy *Combatant, phase *Combat
 	if isCrit {
 		dmg *= 2
 	}
+	// Phase 10 SUB2a — Berserker rage halves incoming weapon damage.
+	// Applied AFTER crit-doubling so the resistance survives crits.
+	if player.Mods.BerserkerRage && player.Mods.PhysicalResistRage {
+		dmg = max(1, dmg/2)
+	}
 	dmg = max(1, dmg)
 
 	if petDeflect {
diff --git a/internal/plugin/dnd.go b/internal/plugin/dnd.go
index 881cef4..f83f369 100644
--- a/internal/plugin/dnd.go
+++ b/internal/plugin/dnd.go
@@ -182,6 +182,11 @@ type DnDCharacter struct {
 	// cooldown (LastSubclassRespecAt) and 500-coin cost.
 	Subclass                 DnDSubclass
 	LastSubclassRespecAt     *time.Time
+	// Phase 10 SUB2a — Berserker Frenzy increments after each rage'd
+	// combat; future class abilities will also tick this. Cleared on
+	// long rest. 5e caps at 6 (death); we let it grow and let consumers
+	// clamp where needed.
+	Exhaustion               int
 	LastRespecAt    *time.Time
 	LastShortRestAt *time.Time
 	LastLongRestAt  *time.Time
@@ -210,7 +215,7 @@ func LoadDnDCharacter(userID id.UserID) (*DnDCharacter, error) {
 		       hp_current, hp_max, temp_hp, armor_class,
 		       pending_setup, auto_migrated, onboarding_sent, armed_ability,
 		       pending_cast, concentration_spell, concentration_expires_at,
-		       subclass, last_subclass_respec_at,
+		       subclass, last_subclass_respec_at, exhaustion,
 		       last_respec_at, last_short_rest_at, last_long_rest_at,
 		       created_at, updated_at
 		FROM dnd_character WHERE user_id = ?`, string(userID))
@@ -223,7 +228,7 @@ func LoadDnDCharacter(userID id.UserID) (*DnDCharacter, error) {
 		&c.HPCurrent, &c.HPMax, &c.TempHP, &c.ArmorClass,
 		&pending, &autoMig, &onboard, &c.ArmedAbility,
 		&c.PendingCast, &c.ConcentrationSpell, &c.ConcentrationExpiresAt,
-		&subclassStr, &c.LastSubclassRespecAt,
+		&subclassStr, &c.LastSubclassRespecAt, &c.Exhaustion,
 		&c.LastRespecAt, &c.LastShortRestAt, &c.LastLongRestAt,
 		&c.CreatedAt, &c.UpdatedAt)
 	if errors.Is(err, sql.ErrNoRows) {
@@ -262,9 +267,9 @@ func SaveDnDCharacter(c *DnDCharacter) error {
 		    hp_current, hp_max, temp_hp, armor_class,
 		    pending_setup, auto_migrated, onboarding_sent, armed_ability,
 		    pending_cast, concentration_spell, concentration_expires_at,
-		    subclass, last_subclass_respec_at,
+		    subclass, last_subclass_respec_at, exhaustion,
 		    last_respec_at, last_short_rest_at, last_long_rest_at, updated_at)
-		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)
+		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)
 		ON CONFLICT(user_id) DO UPDATE SET
 		    race=excluded.race, class=excluded.class,
 		    dnd_level=excluded.dnd_level, dnd_xp=excluded.dnd_xp,
@@ -282,6 +287,7 @@ func SaveDnDCharacter(c *DnDCharacter) error {
 		    concentration_expires_at=excluded.concentration_expires_at,
 		    subclass=excluded.subclass,
 		    last_subclass_respec_at=excluded.last_subclass_respec_at,
+		    exhaustion=excluded.exhaustion,
 		    last_respec_at=excluded.last_respec_at,
 		    last_short_rest_at=excluded.last_short_rest_at,
 		    last_long_rest_at=excluded.last_long_rest_at,
@@ -291,7 +297,7 @@ func SaveDnDCharacter(c *DnDCharacter) error {
 		c.HPCurrent, c.HPMax, c.TempHP, c.ArmorClass,
 		pending, autoMig, onboard, c.ArmedAbility,
 		c.PendingCast, c.ConcentrationSpell, c.ConcentrationExpiresAt,
-		string(c.Subclass), c.LastSubclassRespecAt,
+		string(c.Subclass), c.LastSubclassRespecAt, c.Exhaustion,
 		c.LastRespecAt, c.LastShortRestAt, c.LastLongRestAt)
 	if err != nil {
 		return fmt.Errorf("save dnd_character: %w", err)
diff --git a/internal/plugin/dnd_abilities.go b/internal/plugin/dnd_abilities.go
index 750357e..8a12847 100644
--- a/internal/plugin/dnd_abilities.go
+++ b/internal/plugin/dnd_abilities.go
@@ -27,6 +27,11 @@ type DnDAbility struct {
 	ID          string
 	Name        string
 	Class       DnDClass
+	// Subclass: if non-empty, ability is only available when the player's
+	// subclass matches. Phase 10 adds the first such ability (Berserker
+	// rage). Used by parseAbility/arm gating and by classActiveAbilities
+	// when listing for !arm / !abilities.
+	Subclass    DnDSubclass
 	Resource    string // "stamina", "spell_slot", "favor", etc.
 	Description string
 	// Effect — applied to mods at combat start when armed
@@ -83,17 +88,35 @@ func parseAbility(s string) (DnDAbility, bool) {
 	return DnDAbility{}, false
 }
 
-// classActiveAbilities returns the active abilities a class can know.
+// classActiveAbilities returns the active abilities a class can know,
+// excluding subclass-gated entries (those are listed by characterActiveAbilities).
 func classActiveAbilities(class DnDClass) []DnDAbility {
 	var out []DnDAbility
 	for _, a := range dndActiveAbilities {
-		if a.Class == class {
+		if a.Class == class && a.Subclass == "" {
 			out = append(out, a)
 		}
 	}
 	return out
 }
 
+// characterActiveAbilities returns abilities available to a given character,
+// including their subclass-gated abilities. Used for !arm listing so the
+// Berserker sees `rage` once they've chosen the subclass.
+func characterActiveAbilities(c *DnDCharacter) []DnDAbility {
+	var out []DnDAbility
+	for _, a := range dndActiveAbilities {
+		if a.Class != c.Class {
+			continue
+		}
+		if a.Subclass != "" && a.Subclass != c.Subclass {
+			continue
+		}
+		out = append(out, a)
+	}
+	return out
+}
+
 // ── Resource pool ────────────────────────────────────────────────────────────
 
 // classResourceMax returns (resource_type, max_value) for a class.
@@ -201,6 +224,12 @@ func (p *AdventurePlugin) handleDnDArmCmd(ctx MessageContext, args string) error
 		return p.SendDM(ctx.Sender, fmt.Sprintf(
 			"%s is a %s ability — your class is %s.", ab.Name, titleClass(ab.Class), titleClass(c.Class)))
 	}
+	if ab.Subclass != "" && ab.Subclass != c.Subclass {
+		needed, _ := subclassInfo(ab.Subclass)
+		return p.SendDM(ctx.Sender, fmt.Sprintf(
+			"%s is a %s subclass ability — choose that subclass via `!subclass`.",
+			ab.Name, needed.Display))
+	}
 
 	if c.ArmedAbility != "" {
 		return p.SendDM(ctx.Sender, fmt.Sprintf(
@@ -244,7 +273,7 @@ func (p *AdventurePlugin) handleDnDArmCmd(ctx MessageContext, args string) error
 }
 
 func renderArmList(c *DnDCharacter) string {
-	abilities := classActiveAbilities(c.Class)
+	abilities := characterActiveAbilities(c)
 	var b strings.Builder
 	b.WriteString("**Active Abilities** (pre-arm via `!arm <name>`)\n\n")
 
diff --git a/internal/plugin/dnd_rest.go b/internal/plugin/dnd_rest.go
index 6225e6a..1599ebd 100644
--- a/internal/plugin/dnd_rest.go
+++ b/internal/plugin/dnd_rest.go
@@ -140,6 +140,12 @@ func (p *AdventurePlugin) handleDnDLongRest(ctx MessageContext) error {
 
 	c.HPCurrent = c.HPMax
 	c.TempHP = 0
+	// Phase 10 SUB2a — long rest clears one level of exhaustion (5e: a
+	// long rest clears one). For Berserker who racks up exhaustion via
+	// Frenzy, this is the recovery cadence.
+	if c.Exhaustion > 0 {
+		c.Exhaustion--
+	}
 	now := time.Now().UTC()
 	c.LastLongRestAt = &now
 
diff --git a/internal/plugin/dnd_setup.go b/internal/plugin/dnd_setup.go
index 300755f..d9be989 100644
--- a/internal/plugin/dnd_setup.go
+++ b/internal/plugin/dnd_setup.go
@@ -387,6 +387,7 @@ func (p *AdventurePlugin) handleDnDRespecCmd(ctx MessageContext) error {
 	// cooldown is dropped — at L1 with no class there's nothing to gate.
 	c.Subclass = ""
 	c.LastSubclassRespecAt = nil
+	c.Exhaustion = 0
 	// Save the wipe BEFORE debiting euros (audit fix B). If save fails, the
 	// player's old state survives and they keep their euros — better than
 	// a destructive debit-without-wipe.
diff --git a/internal/plugin/dnd_sheet.go b/internal/plugin/dnd_sheet.go
index 239e656..c4bdfed 100644
--- a/internal/plugin/dnd_sheet.go
+++ b/internal/plugin/dnd_sheet.go
@@ -23,8 +23,8 @@ func (p *AdventurePlugin) handleDnDAbilitiesCmd(ctx MessageContext) error {
 	b.WriteString(fmt.Sprintf("**Class passive — %s**\n  %s\n\n", ab.Name, ab.Description))
 	b.WriteString(fmt.Sprintf("**Race trait**\n  %s\n", ri.Passive))
 
-	// Active abilities (Phase 6)
-	actives := classActiveAbilities(c.Class)
+	// Active abilities (Phase 6 + Phase 10 subclass-gated)
+	actives := characterActiveAbilities(c)
 	if len(actives) > 0 {
 		resType, _ := classResourceMax(c.Class)
 		cur, max, _ := getResource(c.UserID, resType)
diff --git a/internal/plugin/dnd_skills.go b/internal/plugin/dnd_skills.go
index 3d44c08..f3a617d 100644
--- a/internal/plugin/dnd_skills.go
+++ b/internal/plugin/dnd_skills.go
@@ -21,16 +21,17 @@ import (
 type DnDSkill string
 
 const (
-	SkillAthletics     DnDSkill = "athletics"
-	SkillAcrobatics    DnDSkill = "acrobatics"
-	SkillStealth       DnDSkill = "stealth"
-	SkillArcana        DnDSkill = "arcana"
-	SkillInvestigation DnDSkill = "investigation"
-	SkillPerception    DnDSkill = "perception"
-	SkillInsight       DnDSkill = "insight"
-	SkillPersuasion    DnDSkill = "persuasion"
-	SkillIntimidation  DnDSkill = "intimidation"
-	SkillDeception     DnDSkill = "deception"
+	SkillAthletics      DnDSkill = "athletics"
+	SkillAcrobatics     DnDSkill = "acrobatics"
+	SkillStealth        DnDSkill = "stealth"
+	SkillSleightOfHand  DnDSkill = "sleight_of_hand"
+	SkillArcana         DnDSkill = "arcana"
+	SkillInvestigation  DnDSkill = "investigation"
+	SkillPerception     DnDSkill = "perception"
+	SkillInsight        DnDSkill = "insight"
+	SkillPersuasion     DnDSkill = "persuasion"
+	SkillIntimidation   DnDSkill = "intimidation"
+	SkillDeception      DnDSkill = "deception"
 )
 
 type dndSkillInfo struct {
@@ -43,6 +44,7 @@ var dndSkillTable = []dndSkillInfo{
 	{SkillAthletics, "Athletics", "str"},
 	{SkillAcrobatics, "Acrobatics", "dex"},
 	{SkillStealth, "Stealth", "dex"},
+	{SkillSleightOfHand, "Sleight of Hand", "dex"},
 	{SkillArcana, "Arcana", "int"},
 	{SkillInvestigation, "Investigation", "int"},
 	{SkillPerception, "Perception", "wis"},
@@ -136,6 +138,54 @@ func statValue(c *DnDCharacter, stat string) int {
 	return 10
 }
 
+// subclassSkillBonus returns the additive bonus from a subclass ability
+// for a given skill. Phase 10 SUB2a:
+//
+//	Champion (L7+) Remarkable Athlete: +½ proficiency bonus (rounded down)
+//	  to STR/DEX/CON skill checks. Approximation of 5e's "+½ prof to
+//	  checks not already proficient"; we don't track per-skill prof yet.
+//	Thief (L5+) Fast Hands: +5 to Sleight of Hand. Stand-in for 5e's
+//	  "bonus action: SoH check" — out-of-combat utility flattened into a
+//	  raw skill bonus.
+func subclassSkillBonus(c *DnDCharacter, info dndSkillInfo) int {
+	if c == nil || c.Subclass == "" {
+		return 0
+	}
+	switch c.Subclass {
+	case SubclassChampion:
+		if c.Level >= 7 {
+			switch info.Stat {
+			case "str", "dex", "con":
+				return proficiencyBonus(c.Level) / 2
+			}
+		}
+	case SubclassThief:
+		if c.Level >= 5 && info.Key == SkillSleightOfHand {
+			return 5
+		}
+	}
+	return 0
+}
+
+// subclassSkillAdvantage reports whether the player rolls with advantage
+// (best of two d20s) on this skill check. Phase 10 SUB2a:
+//
+//	Thief (L7+) Supreme Sneak: advantage on Stealth (5e gates this on
+//	  half-speed movement; we don't track movement speed, so we apply
+//	  unconditionally — approachability cut).
+func subclassSkillAdvantage(c *DnDCharacter, info dndSkillInfo) bool {
+	if c == nil || c.Subclass == "" {
+		return false
+	}
+	switch c.Subclass {
+	case SubclassThief:
+		if c.Level >= 7 && info.Key == SkillStealth {
+			return true
+		}
+	}
+	return false
+}
+
 // raceSkillBonus returns the per-skill bonus from a player's race.
 // Half-Elf gets +1 to every skill (rough mapping of "two bonus skill profs").
 // Tiefling gets +2 to CHA-based skills (matches the doc's "+bonus on CHA checks").
@@ -151,11 +201,20 @@ func raceSkillBonus(c *DnDCharacter, info dndSkillInfo) int {
 	return 0
 }
 
-// performSkillCheck rolls the d20 and computes the result.
+// performSkillCheck rolls the d20 and computes the result. Subclass
+// effects (Phase 10 SUB2a) apply additive bonuses and may grant advantage
+// (best of two d20s).
 func performSkillCheck(c *DnDCharacter, skill DnDSkill, dc int) SkillCheckResult {
 	info, _ := skillInfo(skill)
-	mod := abilityModifier(statValue(c, info.Stat)) + raceSkillBonus(c, info)
+	mod := abilityModifier(statValue(c, info.Stat)) +
+		raceSkillBonus(c, info) +
+		subclassSkillBonus(c, info)
 	roll := 1 + rand.IntN(20)
+	if subclassSkillAdvantage(c, info) {
+		if alt := 1 + rand.IntN(20); alt > roll {
+			roll = alt
+		}
+	}
 	res := SkillCheckResult{Skill: skill, DC: dc, Roll: roll, Mod: mod}
 
 	switch roll {
diff --git a/internal/plugin/dnd_skills_test.go b/internal/plugin/dnd_skills_test.go
index 0fc93c6..98ce21a 100644
--- a/internal/plugin/dnd_skills_test.go
+++ b/internal/plugin/dnd_skills_test.go
@@ -7,7 +7,8 @@ import (
 func TestSkillTableComplete(t *testing.T) {
 	expectedStats := map[DnDSkill]string{
 		SkillAthletics: "str", SkillAcrobatics: "dex", SkillStealth: "dex",
-		SkillArcana: "int", SkillInvestigation: "int",
+		SkillSleightOfHand: "dex",
+		SkillArcana:        "int", SkillInvestigation: "int",
 		SkillPerception: "wis", SkillInsight: "wis",
 		SkillPersuasion: "cha", SkillIntimidation: "cha", SkillDeception: "cha",
 	}
diff --git a/internal/plugin/dnd_subclass_combat.go b/internal/plugin/dnd_subclass_combat.go
new file mode 100644
index 0000000..ad2093b
--- /dev/null
+++ b/internal/plugin/dnd_subclass_combat.go
@@ -0,0 +1,73 @@
+package plugin
+
+// Phase 10 SUB2a — subclass combat hooks.
+//
+// applySubclassPassives layers subclass-driven flags onto CombatModifiers
+// the same way applyClassPassives does. Called from combat_bridge after
+// applyClassPassives so subclass effects can stack on top of (or override)
+// class baseline.
+//
+// Subclass active abilities (currently just Berserker's rage) are
+// registered via init() into dndActiveAbilities below, gated by
+// DnDAbility.Subclass.
+
+func applySubclassPassives(stats *CombatStats, mods *CombatModifiers, c *DnDCharacter) {
+	if c == nil || c.Subclass == "" {
+		return
+	}
+	switch c.Subclass {
+	case SubclassChampion:
+		// L5 Improved Critical: crit on nat 19+. SUB3 Superior Critical
+		// (L15) will lower this to 18.
+		if c.Level >= 5 {
+			mods.CritThreshold = 19
+		}
+	}
+}
+
+func init() {
+	// Berserker rage — active ability that piggybacks on the Fighter
+	// stamina pool. 5e specs 3 uses/long-rest as a separate pool, but
+	// stamina is already sized at 3 for Fighter and the design's
+	// "approachability" constraint preferred reusing the existing pool
+	// over introducing per-subclass resource types in SUB2a.
+	//
+	// While armed and fired:
+	//   - +2 flat damage per hit (RageMeleeDmg)
+	//   - incoming weapon damage halved (PhysicalResistRage)
+	//   - +50% damage multiplier for Frenzy approximation
+	//     (one-shot combat can't model "1 bonus attack per turn" literally)
+	//
+	// Post-combat exhaustion increment lives in
+	// persistDnDPostCombatSubclass — Frenzy specs +1 exhaustion after rage
+	// ends, and in our model rage spans the whole one-shot combat so we
+	// always tick exhaustion when rage fired.
+	dndActiveAbilities["rage"] = DnDAbility{
+		ID:          "rage",
+		Name:        "Rage",
+		Class:       ClassFighter,
+		Subclass:    SubclassBerserker,
+		Resource:    "stamina",
+		Description: "Enter rage for the next combat: +2 damage per hit, halve incoming weapon damage, Frenzy bonus attack approximation. +1 exhaustion after.",
+		Apply: func(c *DnDCharacter, mods *CombatModifiers) {
+			mods.BerserkerRage = true
+			mods.RageMeleeDmg = 2
+			mods.PhysicalResistRage = true
+			mods.FrenzyDmgBonus = 0.5
+		},
+	}
+}
+
+// persistDnDPostCombatSubclass handles end-of-combat subclass bookkeeping.
+// Currently: increment Exhaustion if Berserker rage fired. Called from
+// combat_bridge after the combat result is computed.
+//
+// raged is computed as (mods.BerserkerRage at combat-start time) — pass it
+// through from the caller where the mods value is still in scope.
+func persistDnDPostCombatSubclass(c *DnDCharacter, raged bool) error {
+	if c == nil || !raged {
+		return nil
+	}
+	c.Exhaustion++
+	return SaveDnDCharacter(c)
+}
diff --git a/internal/plugin/dnd_subclass_combat_test.go b/internal/plugin/dnd_subclass_combat_test.go
new file mode 100644
index 0000000..1ff4d39
--- /dev/null
+++ b/internal/plugin/dnd_subclass_combat_test.go
@@ -0,0 +1,403 @@
+package plugin
+
+import (
+	"testing"
+
+	"maunium.net/go/mautrix/id"
+)
+
+// Phase 10 SUB2a-i — subclass combat hooks (Champion, Berserker, Thief).
+
+// ── applySubclassPassives ────────────────────────────────────────────────
+
+func TestApplySubclassPassives_ChampionLowersCritThreshold(t *testing.T) {
+	c := &DnDCharacter{Class: ClassFighter, Subclass: SubclassChampion, Level: 5}
+	stats := &CombatStats{}
+	mods := &CombatModifiers{DamageReduct: 1.0}
+	applySubclassPassives(stats, mods, c)
+	if mods.CritThreshold != 19 {
+		t.Errorf("CritThreshold = %d, want 19", mods.CritThreshold)
+	}
+}
+
+func TestApplySubclassPassives_NoChampionPreL5(t *testing.T) {
+	// Subclass selection only happens at L5+, but if state ever drifts
+	// (race-condition with level reset), the passive must not fire below
+	// the gating level.
+	c := &DnDCharacter{Class: ClassFighter, Subclass: SubclassChampion, Level: 4}
+	mods := &CombatModifiers{DamageReduct: 1.0}
+	applySubclassPassives(&CombatStats{}, mods, c)
+	if mods.CritThreshold != 0 {
+		t.Errorf("CritThreshold = %d, want 0 (default) at L4", mods.CritThreshold)
+	}
+}
+
+func TestApplySubclassPassives_NoSubclassNoEffect(t *testing.T) {
+	c := &DnDCharacter{Class: ClassFighter, Level: 5}
+	mods := &CombatModifiers{DamageReduct: 1.0}
+	applySubclassPassives(&CombatStats{}, mods, c)
+	if mods.CritThreshold != 0 {
+		t.Errorf("CritThreshold should default to 0 with no subclass; got %d", mods.CritThreshold)
+	}
+}
+
+// ── Rage active ability ──────────────────────────────────────────────────
+
+func TestRageAbility_ApplySetsAllFlags(t *testing.T) {
+	ab, ok := dndActiveAbilities["rage"]
+	if !ok {
+		t.Fatal("rage ability not registered")
+	}
+	if ab.Class != ClassFighter || ab.Subclass != SubclassBerserker {
+		t.Errorf("rage gating: class=%s subclass=%s, want fighter/berserker",
+			ab.Class, ab.Subclass)
+	}
+	if ab.Resource != "stamina" {
+		t.Errorf("rage resource = %s, want stamina", ab.Resource)
+	}
+
+	c := &DnDCharacter{Class: ClassFighter, Subclass: SubclassBerserker, Level: 5}
+	mods := &CombatModifiers{DamageReduct: 1.0}
+	ab.Apply(c, mods)
+	if !mods.BerserkerRage {
+		t.Error("BerserkerRage not set")
+	}
+	if mods.RageMeleeDmg != 2 {
+		t.Errorf("RageMeleeDmg = %d, want 2", mods.RageMeleeDmg)
+	}
+	if !mods.PhysicalResistRage {
+		t.Error("PhysicalResistRage not set")
+	}
+	if mods.FrenzyDmgBonus <= 0 {
+		t.Errorf("FrenzyDmgBonus = %v, want > 0", mods.FrenzyDmgBonus)
+	}
+}
+
+// ── Post-combat exhaustion ───────────────────────────────────────────────
+
+func TestPersistDnDPostCombatSubclass_RagedIncrementsExhaustion(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@rage_exh:example")
+	if err := createAdvCharacter(uid, "rage_exh"); err != nil {
+		t.Fatal(err)
+	}
+	c := &DnDCharacter{
+		UserID: uid, Race: RaceOrc, Class: ClassFighter, Subclass: SubclassBerserker,
+		Level: 6, STR: 16, DEX: 12, CON: 14, INT: 8, WIS: 10, CHA: 10,
+		HPMax: 30, HPCurrent: 30, ArmorClass: 16,
+	}
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatal(err)
+	}
+	if err := persistDnDPostCombatSubclass(c, true); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := LoadDnDCharacter(uid)
+	if got.Exhaustion != 1 {
+		t.Errorf("Exhaustion after raged combat = %d, want 1", got.Exhaustion)
+	}
+	// Second raged combat → 2.
+	if err := persistDnDPostCombatSubclass(got, true); err != nil {
+		t.Fatal(err)
+	}
+	got2, _ := LoadDnDCharacter(uid)
+	if got2.Exhaustion != 2 {
+		t.Errorf("Exhaustion after 2 raged combats = %d, want 2", got2.Exhaustion)
+	}
+}
+
+func TestPersistDnDPostCombatSubclass_NoRageNoIncrement(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@no_rage_exh:example")
+	if err := createAdvCharacter(uid, "no_rage"); err != nil {
+		t.Fatal(err)
+	}
+	c := &DnDCharacter{
+		UserID: uid, Race: RaceHuman, Class: ClassFighter, Subclass: SubclassChampion,
+		Level: 6, STR: 16, DEX: 12, CON: 14, INT: 8, WIS: 10, CHA: 10,
+		HPMax: 30, HPCurrent: 30, ArmorClass: 16, Exhaustion: 3,
+	}
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatal(err)
+	}
+	if err := persistDnDPostCombatSubclass(c, false); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := LoadDnDCharacter(uid)
+	if got.Exhaustion != 3 {
+		t.Errorf("Exhaustion changed without rage: %d, want 3", got.Exhaustion)
+	}
+}
+
+// ── End-to-end SimulateCombat with rage flags ────────────────────────────
+
+func ragingPlayer() Combatant {
+	return Combatant{
+		Name: "Rager", IsPlayer: true,
+		Stats: CombatStats{
+			MaxHP: 100, Attack: 15, Defense: 8, Speed: 10,
+			CritRate: 0.05, DodgeRate: 0.05, BlockRate: 0.05,
+		},
+		Mods: CombatModifiers{
+			DamageReduct: 1.0,
+			BerserkerRage: true, RageMeleeDmg: 2,
+			PhysicalResistRage: true, FrenzyDmgBonus: 0.5,
+		},
+	}
+}
+
+func calmPlayer() Combatant {
+	return Combatant{
+		Name: "Calm", IsPlayer: true,
+		Stats: CombatStats{
+			MaxHP: 100, Attack: 15, Defense: 8, Speed: 10,
+			CritRate: 0.05, DodgeRate: 0.05, BlockRate: 0.05,
+		},
+		Mods: CombatModifiers{DamageReduct: 1.0},
+	}
+}
+
+func toughEnemy() Combatant {
+	// Sized so the calm baseline wins ~half the time — gives rage room
+	// to push the win rate noticeably higher.
+	return Combatant{
+		Name: "Brute",
+		Stats: CombatStats{
+			MaxHP: 110, Attack: 18, Defense: 10, Speed: 8,
+			CritRate: 0.05, DodgeRate: 0.05, BlockRate: 0.05,
+		},
+		Mods: CombatModifiers{DamageBonus: 0, DamageReduct: 1.0},
+	}
+}
+
+// Probabilistic: raging Berserker should win more often than the calm
+// baseline against an enemy strong enough that the calm player isn't
+// already maxing out wins.
+func TestSimulateCombat_RageImprovesWinRate(t *testing.T) {
+	const trials = 2000
+	calmWins, rageWins := 0, 0
+	for i := 0; i < trials; i++ {
+		if SimulateCombat(calmPlayer(), toughEnemy(), defaultCombatPhases).PlayerWon {
+			calmWins++
+		}
+		if SimulateCombat(ragingPlayer(), toughEnemy(), defaultCombatPhases).PlayerWon {
+			rageWins++
+		}
+	}
+	// Demand at least a 5-percentage-point lift to keep the test honest
+	// without making it flaky on tail RNG.
+	margin := rageWins - calmWins
+	if margin < trials/20 {
+		t.Errorf("rage win-rate lift too small: calm=%d rage=%d (margin %d, want >=%d)",
+			calmWins, rageWins, margin, trials/20)
+	}
+}
+
+// ── Skill bonuses ────────────────────────────────────────────────────────
+
+func TestSubclassSkillBonus_ChampionRemarkableAthlete(t *testing.T) {
+	c := &DnDCharacter{Class: ClassFighter, Subclass: SubclassChampion, Level: 7}
+	athletics, _ := skillInfo(SkillAthletics)
+	stealth, _ := skillInfo(SkillStealth) // dex
+	arcana, _ := skillInfo(SkillArcana)   // int — should NOT get the bonus
+	// L7 prof = 3, half = 1.
+	if got := subclassSkillBonus(c, athletics); got != 1 {
+		t.Errorf("Athletics (str) bonus = %d, want 1", got)
+	}
+	if got := subclassSkillBonus(c, stealth); got != 1 {
+		t.Errorf("Stealth (dex) bonus = %d, want 1", got)
+	}
+	if got := subclassSkillBonus(c, arcana); got != 0 {
+		t.Errorf("Arcana (int) bonus = %d, want 0 (Remarkable Athlete is STR/DEX/CON only)", got)
+	}
+}
+
+func TestSubclassSkillBonus_ChampionPreL7NoBonus(t *testing.T) {
+	c := &DnDCharacter{Class: ClassFighter, Subclass: SubclassChampion, Level: 6}
+	athletics, _ := skillInfo(SkillAthletics)
+	if got := subclassSkillBonus(c, athletics); got != 0 {
+		t.Errorf("L6 Champion bonus = %d, want 0 (Remarkable Athlete needs L7)", got)
+	}
+}
+
+func TestSubclassSkillBonus_ThiefFastHands(t *testing.T) {
+	c := &DnDCharacter{Class: ClassRogue, Subclass: SubclassThief, Level: 5}
+	soh, _ := skillInfo(SkillSleightOfHand)
+	stealth, _ := skillInfo(SkillStealth)
+	if got := subclassSkillBonus(c, soh); got != 5 {
+		t.Errorf("Thief SoH bonus = %d, want 5", got)
+	}
+	if got := subclassSkillBonus(c, stealth); got != 0 {
+		t.Errorf("Thief stealth bonus from Fast Hands = %d, want 0 (FH is SoH only)", got)
+	}
+}
+
+func TestSubclassSkillAdvantage_ThiefSupremeSneak(t *testing.T) {
+	c := &DnDCharacter{Class: ClassRogue, Subclass: SubclassThief, Level: 7}
+	stealth, _ := skillInfo(SkillStealth)
+	soh, _ := skillInfo(SkillSleightOfHand)
+	if !subclassSkillAdvantage(c, stealth) {
+		t.Error("L7 Thief should have advantage on Stealth")
+	}
+	if subclassSkillAdvantage(c, soh) {
+		t.Error("Supreme Sneak should not grant advantage on non-Stealth skills")
+	}
+}
+
+func TestSubclassSkillAdvantage_PreL7No(t *testing.T) {
+	c := &DnDCharacter{Class: ClassRogue, Subclass: SubclassThief, Level: 6}
+	stealth, _ := skillInfo(SkillStealth)
+	if subclassSkillAdvantage(c, stealth) {
+		t.Error("L6 Thief should not yet have Stealth advantage")
+	}
+}
+
+// Statistical: Thief L7 stealth average should beat plain rogue by a wide
+// margin (advantage = best of two d20s, expected ≈ 13.83 vs 10.5).
+func TestPerformSkillCheck_StealthAdvantageStatistical(t *testing.T) {
+	const trials = 5000
+	plainRogue := &DnDCharacter{
+		Class: ClassRogue, Level: 7, DEX: 14, // mod +2
+	}
+	thief := &DnDCharacter{
+		Class: ClassRogue, Subclass: SubclassThief, Level: 7, DEX: 14,
+	}
+	plainTotal, thiefTotal := 0, 0
+	for i := 0; i < trials; i++ {
+		plainTotal += performSkillCheck(plainRogue, SkillStealth, 15).Roll
+		thiefTotal += performSkillCheck(thief, SkillStealth, 15).Roll
+	}
+	plainAvg := float64(plainTotal) / float64(trials)
+	thiefAvg := float64(thiefTotal) / float64(trials)
+	// Plain ≈ 10.5; Thief ≈ 13.8. Pick a margin that's robust.
+	if thiefAvg-plainAvg < 2.0 {
+		t.Errorf("Thief stealth roll average not meaningfully higher: plain=%.2f thief=%.2f", plainAvg, thiefAvg)
+	}
+}
+
+// ── !arm rage gating ─────────────────────────────────────────────────────
+
+func TestArmRage_BlockedForNonBerserker(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@arm_rage_block:example")
+	if err := createAdvCharacter(uid, "block"); err != nil {
+		t.Fatal(err)
+	}
+	c := &DnDCharacter{
+		UserID: uid, Race: RaceHuman, Class: ClassFighter, Subclass: SubclassChampion,
+		Level: 6, STR: 16, DEX: 12, CON: 14, INT: 8, WIS: 10, CHA: 10,
+		HPMax: 30, HPCurrent: 30, ArmorClass: 16,
+	}
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatal(err)
+	}
+	if err := initResources(uid, ClassFighter); err != nil {
+		t.Fatal(err)
+	}
+
+	p := &AdventurePlugin{euro: &EuroPlugin{}}
+	if err := p.handleDnDArmCmd(MessageContext{Sender: uid}, "rage"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := LoadDnDCharacter(uid)
+	if got.ArmedAbility == "rage" {
+		t.Error("non-Berserker should not be able to arm rage")
+	}
+}
+
+func TestArmRage_AllowedForBerserker(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@arm_rage_ok:example")
+	if err := createAdvCharacter(uid, "ok"); err != nil {
+		t.Fatal(err)
+	}
+	c := &DnDCharacter{
+		UserID: uid, Race: RaceOrc, Class: ClassFighter, Subclass: SubclassBerserker,
+		Level: 5, STR: 16, DEX: 12, CON: 14, INT: 8, WIS: 10, CHA: 10,
+		HPMax: 30, HPCurrent: 30, ArmorClass: 16,
+	}
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatal(err)
+	}
+	if err := initResources(uid, ClassFighter); err != nil {
+		t.Fatal(err)
+	}
+
+	p := &AdventurePlugin{euro: &EuroPlugin{}}
+	if err := p.handleDnDArmCmd(MessageContext{Sender: uid}, "rage"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := LoadDnDCharacter(uid)
+	if got.ArmedAbility != "rage" {
+		t.Errorf("ArmedAbility = %q, want rage", got.ArmedAbility)
+	}
+}
+
+// ── Long rest decrements exhaustion ──────────────────────────────────────
+
+func TestLongRest_ClearsOneExhaustion(t *testing.T) {
+	c := &DnDCharacter{
+		UserID: "@x:example", Class: ClassFighter, Level: 5,
+		HPMax: 30, HPCurrent: 5, Exhaustion: 3,
+	}
+	// Replicate the long-rest effect: HP top-up + Exhaustion-- (the path
+	// in dnd_rest.go we updated). Pure-state test — no DM or DB.
+	if c.Exhaustion > 0 {
+		c.Exhaustion--
+	}
+	if c.Exhaustion != 2 {
+		t.Errorf("Exhaustion after long rest = %d, want 2", c.Exhaustion)
+	}
+}
+
+// ── Schema roundtrip ─────────────────────────────────────────────────────
+
+func TestExhaustion_SchemaRoundTrip(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@exh_rt:example")
+	if err := createAdvCharacter(uid, "exh_rt"); err != nil {
+		t.Fatal(err)
+	}
+	c := &DnDCharacter{
+		UserID: uid, Race: RaceOrc, Class: ClassFighter, Subclass: SubclassBerserker,
+		Level: 5, STR: 16, DEX: 12, CON: 14, INT: 8, WIS: 10, CHA: 10,
+		HPMax: 30, HPCurrent: 30, ArmorClass: 16, Exhaustion: 4,
+	}
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatal(err)
+	}
+	got, err := LoadDnDCharacter(uid)
+	if err != nil || got == nil {
+		t.Fatalf("load: %v %v", got, err)
+	}
+	if got.Exhaustion != 4 {
+		t.Errorf("Exhaustion roundtrip: got %d, want 4", got.Exhaustion)
+	}
+}
+
+// Surface-level sanity: rage shows up in characterActiveAbilities for a
+// Berserker but not a Champion. Tests the gating helper directly so we
+// don't need the resource-pool DB read that renderArmList does.
+func TestCharacterActiveAbilities_RageVisibility(t *testing.T) {
+	berserker := &DnDCharacter{
+		Class: ClassFighter, Subclass: SubclassBerserker, Level: 5,
+	}
+	champion := &DnDCharacter{
+		Class: ClassFighter, Subclass: SubclassChampion, Level: 5,
+	}
+	hasRage := func(list []DnDAbility) bool {
+		for _, a := range list {
+			if a.ID == "rage" {
+				return true
+			}
+		}
+		return false
+	}
+	if !hasRage(characterActiveAbilities(berserker)) {
+		t.Error("Berserker should have rage in active-ability list")
+	}
+	if hasRage(characterActiveAbilities(champion)) {
+		t.Error("Champion should not have rage in active-ability list")
+	}
+}
+