diff --git a/internal/plugin/dnd_spell_combat.go b/internal/plugin/dnd_spell_combat.go
index 44bf4b4..7fea19f 100644
--- a/internal/plugin/dnd_spell_combat.go
+++ b/internal/plugin/dnd_spell_combat.go
@@ -97,6 +97,19 @@ func applyMageSubclassSpellHooks(c *DnDCharacter, spell SpellDefinition, slotLev
 			}
 			mods.SpellPreDamage += bonus
 		}
+		// Phase 10 SUB3b-i — L10 Overchannel: maximize damage dice on a
+		// 1st–5th-level spell. We don't track per-die rolls here (damage was
+		// rolled in the apply* path above), so we proxy max-vs-avg as +50%
+		// to SpellPreDamage on a leveled cast. 5e gates this to "1st–5th
+		// level" — slot 6+ wouldn't get max dice — and includes a 2d12
+		// necrotic self-damage drawback per cast above the first per long
+		// rest. Self-damage is omitted here: in our model the Mage queues
+		// at most one cast per fight, so the "first per rest" exemption
+		// almost always applies. L15 Sculptural Mastery is AoE-friendly-fire
+		// only — skipped (same reason SUB2b skipped Sculpt Spells).
+		if c.Level >= 10 && slotLevel >= 1 && slotLevel <= 5 {
+			mods.SpellPreDamage = (mods.SpellPreDamage * 3) / 2
+		}
 	case SubclassNecromancy:
 		// L5 Grim Harvest stash — heal applied post-combat iff this spell
 		// landed the killing blow. Cantrip kills count as L1 for the heal
diff --git a/internal/plugin/dnd_subclass_combat.go b/internal/plugin/dnd_subclass_combat.go
index bdd7bf5..1b71e3e 100644
--- a/internal/plugin/dnd_subclass_combat.go
+++ b/internal/plugin/dnd_subclass_combat.go
@@ -101,6 +101,46 @@ func applySubclassPassives(stats *CombatStats, mods *CombatModifiers, c *DnDChar
 			}
 			mods.ArcaneWardHP = ward
 		}
+		// Phase 10 SUB3b-i — L10 Spell Resistance: 5e gives advantage on
+		// saves vs. spells *and* resistance to spell damage. Our 1v1 enemies
+		// rarely force spell saves, so the "advantage" half is largely inert;
+		// we collapse the effect to a flat 8% incoming-damage reduction
+		// (DamageReduct is multiplicative, so 0.92 = ~8% off everything,
+		// which is close to "resistance against the spell-damage subset").
+		if c.Level >= 10 {
+			mods.DamageReduct *= 0.92
+		}
+		// Phase 10 SUB3b-i — L15 Spell Reflection: 5e lets a successful
+		// counterspell redirect the spell back at the caster. We don't model
+		// counterspell (reaction primitive deferred to Phase 11), so we ride
+		// the ReflectNext channel — the first incoming hit reflects 30% of
+		// its damage back. Closest in-engine analogue to "the magic hits the
+		// caster instead".
+		if c.Level >= 15 {
+			mods.ReflectNext += 0.30
+		}
+	case SubclassNecromancy:
+		// Phase 10 SUB3b-i — L15 Improved Undead Thralls. 5e: undead thralls
+		// gain +CON mod to HP and attack damage. We don't model an Animate
+		// Dead summoning system (SUB2b skipped Undead Thralls for the same
+		// reason), but the L15 capstone is too central to skip — proxy a
+		// permanent skeletal minion via the PetAttack channel. CON-mod scales
+		// dmg, mirroring the 5e formula. L10 Command Undead's combat surface
+		// is folded into grimHarvestHeal (deeper authority over death = more
+		// life harvested per spell-kill); see dnd_subclass_combat.go below.
+		if c.Level >= 15 {
+			conMod := abilityModifier(c.CON)
+			if conMod < 0 {
+				conMod = 0
+			}
+			thrallDmg := 6 + conMod
+			if mods.PetAttackProc < 0.30 {
+				mods.PetAttackProc = 0.30
+			}
+			if mods.PetAttackDmg < thrallDmg {
+				mods.PetAttackDmg = thrallDmg
+			}
+		}
 	case SubclassAssassin:
 		// L5 Assassinate: advantage on the opening strike + bonus damage
 		// stacked on top of the Rogue's existing Sneak Attack auto-crit
@@ -398,9 +438,17 @@ func grimHarvestHeal(c *DnDCharacter, result CombatResult, mods CombatModifiers)
 			break
 		}
 	}
-	heal := 2 * mods.GrimHarvestSlot
+	// Phase 10 SUB3b-i — L10 Command Undead. The 5e ability is "take control
+	// of any undead", which has no surface in our 1v1 combat (no allies to
+	// hand summons over to). We re-fluff it here as deeper authority over
+	// death amplifying the harvest itself: multipliers tick up by 1 at L10
+	// (2× → 3× non-necrotic, 3× → 4× necrotic).
+	mult := 2
 	if mods.GrimHarvestNecrotic {
-		heal = 3 * mods.GrimHarvestSlot
+		mult = 3
 	}
-	return heal
+	if c.Level >= 10 {
+		mult++
+	}
+	return mult * mods.GrimHarvestSlot
 }
diff --git a/internal/plugin/dnd_subclass_mage_test.go b/internal/plugin/dnd_subclass_mage_test.go
index 889a77c..f39ddc1 100644
--- a/internal/plugin/dnd_subclass_mage_test.go
+++ b/internal/plugin/dnd_subclass_mage_test.go
@@ -238,3 +238,138 @@ func TestPersistDnDPostCombatSubclass_GrimHarvestApplies(t *testing.T) {
 		t.Errorf("HP after Grim Harvest = %d, want 16 (10 + 6)", got.HPCurrent)
 	}
 }
+
+// ── Phase 10 SUB3b-i — Mage L10/L15 ─────────────────────────────────────
+
+func TestEvocation_OverchannelL10MaximizesLeveledDamage(t *testing.T) {
+	spell, _ := lookupSpell("magic_missile") // school evocation, leveled
+	c := &DnDCharacter{Class: ClassMage, Subclass: SubclassEvocation, Level: 10, INT: 18}
+	mods := &CombatModifiers{SpellPreDamage: 20}
+	applyMageSubclassSpellHooks(c, spell, 3, mods)
+	// magic_missile.school is "evocation", so Empowered Evocation also fires
+	// at L10 (gated >=L7): +INT mod 4 → SpellPreDamage = 24, then Overchannel
+	// ×1.5 → 36.
+	if mods.SpellPreDamage != 36 {
+		t.Errorf("Overchannel L10 leveled SpellPreDamage = %d, want 36 ((20+4)*3/2)", mods.SpellPreDamage)
+	}
+}
+
+func TestEvocation_OverchannelSkipsCantrip(t *testing.T) {
+	spell, _ := lookupSpell("fire_bolt") // school evocation, cantrip (Level 0)
+	c := &DnDCharacter{Class: ClassMage, Subclass: SubclassEvocation, Level: 10, INT: 18}
+	mods := &CombatModifiers{SpellPreDamage: 20}
+	applyMageSubclassSpellHooks(c, spell, 0, mods)
+	// Empowered Evocation +4, Overchannel skipped (slot < 1).
+	if mods.SpellPreDamage != 24 {
+		t.Errorf("Overchannel should skip cantrip (slot 0): SpellPreDamage = %d, want 24", mods.SpellPreDamage)
+	}
+}
+
+func TestEvocation_OverchannelSkipsAboveSlot5(t *testing.T) {
+	spell, _ := lookupSpell("magic_missile")
+	c := &DnDCharacter{Class: ClassMage, Subclass: SubclassEvocation, Level: 10, INT: 18}
+	mods := &CombatModifiers{SpellPreDamage: 20}
+	applyMageSubclassSpellHooks(c, spell, 6, mods)
+	// 5e Overchannel caps at slot 5; slot 6 just gets Empowered Evocation.
+	if mods.SpellPreDamage != 24 {
+		t.Errorf("Overchannel should not fire on slot 6: SpellPreDamage = %d, want 24", mods.SpellPreDamage)
+	}
+}
+
+func TestEvocation_OverchannelPreL10Skipped(t *testing.T) {
+	spell, _ := lookupSpell("magic_missile")
+	c := &DnDCharacter{Class: ClassMage, Subclass: SubclassEvocation, Level: 9, INT: 18}
+	mods := &CombatModifiers{SpellPreDamage: 20}
+	applyMageSubclassSpellHooks(c, spell, 3, mods)
+	if mods.SpellPreDamage != 24 {
+		t.Errorf("Overchannel pre-L10 should not fire: SpellPreDamage = %d, want 24", mods.SpellPreDamage)
+	}
+}
+
+func TestAbjuration_SpellResistanceL10ReducesDamage(t *testing.T) {
+	c := &DnDCharacter{Class: ClassMage, Subclass: SubclassAbjuration, Level: 10}
+	mods := &CombatModifiers{DamageReduct: 1.0}
+	applySubclassPassives(&CombatStats{}, mods, c)
+	if mods.DamageReduct >= 1.0 || mods.DamageReduct < 0.91 || mods.DamageReduct > 0.93 {
+		t.Errorf("Abjuration L10 DamageReduct = %f, want ~0.92", mods.DamageReduct)
+	}
+}
+
+func TestAbjuration_SpellResistancePreL10Skipped(t *testing.T) {
+	c := &DnDCharacter{Class: ClassMage, Subclass: SubclassAbjuration, Level: 9}
+	mods := &CombatModifiers{DamageReduct: 1.0}
+	applySubclassPassives(&CombatStats{}, mods, c)
+	if mods.DamageReduct != 1.0 {
+		t.Errorf("Abjuration pre-L10 DamageReduct = %f, want 1.0", mods.DamageReduct)
+	}
+}
+
+func TestAbjuration_SpellReflectionL15(t *testing.T) {
+	c := &DnDCharacter{Class: ClassMage, Subclass: SubclassAbjuration, Level: 15}
+	mods := &CombatModifiers{DamageReduct: 1.0}
+	applySubclassPassives(&CombatStats{}, mods, c)
+	if mods.ReflectNext < 0.29 || mods.ReflectNext > 0.31 {
+		t.Errorf("Abjuration L15 ReflectNext = %f, want ~0.30", mods.ReflectNext)
+	}
+}
+
+func TestAbjuration_SpellReflectionPreL15Skipped(t *testing.T) {
+	c := &DnDCharacter{Class: ClassMage, Subclass: SubclassAbjuration, Level: 14}
+	mods := &CombatModifiers{DamageReduct: 1.0}
+	applySubclassPassives(&CombatStats{}, mods, c)
+	if mods.ReflectNext != 0 {
+		t.Errorf("Abjuration pre-L15 ReflectNext = %f, want 0", mods.ReflectNext)
+	}
+}
+
+func TestNecromancy_CommandUndeadL10AmplifiesHarvest(t *testing.T) {
+	c := &DnDCharacter{Class: ClassMage, Subclass: SubclassNecromancy, Level: 10}
+	result := CombatResult{
+		PlayerWon: true,
+		Events:    []CombatEvent{{Action: "spell_cast", EnemyHP: 0}},
+	}
+	// Non-necrotic at L10: 3× slot (was 2×).
+	mods := CombatModifiers{GrimHarvestSlot: 3}
+	if got := grimHarvestHeal(c, result, mods); got != 9 {
+		t.Errorf("L10 non-necrotic Grim Harvest = %d, want 9 (3× slot)", got)
+	}
+	// Necrotic at L10: 4× slot (was 3×).
+	mods = CombatModifiers{GrimHarvestSlot: 2, GrimHarvestNecrotic: true}
+	if got := grimHarvestHeal(c, result, mods); got != 8 {
+		t.Errorf("L10 necrotic Grim Harvest = %d, want 8 (4× slot)", got)
+	}
+}
+
+func TestNecromancy_ImprovedUndeadThrallsL15SetsPetAttack(t *testing.T) {
+	c := &DnDCharacter{Class: ClassMage, Subclass: SubclassNecromancy, Level: 15, CON: 14} // +2 mod
+	mods := &CombatModifiers{DamageReduct: 1.0}
+	applySubclassPassives(&CombatStats{}, mods, c)
+	if mods.PetAttackProc < 0.29 || mods.PetAttackProc > 0.31 {
+		t.Errorf("Necromancer L15 PetAttackProc = %f, want ~0.30", mods.PetAttackProc)
+	}
+	if mods.PetAttackDmg != 8 { // 6 + CON mod 2
+		t.Errorf("Necromancer L15 CON 14 PetAttackDmg = %d, want 8 (6 + 2)", mods.PetAttackDmg)
+	}
+}
+
+func TestNecromancy_ImprovedUndeadThrallsPreL15Skipped(t *testing.T) {
+	c := &DnDCharacter{Class: ClassMage, Subclass: SubclassNecromancy, Level: 14, CON: 14}
+	mods := &CombatModifiers{DamageReduct: 1.0}
+	applySubclassPassives(&CombatStats{}, mods, c)
+	if mods.PetAttackProc != 0 || mods.PetAttackDmg != 0 {
+		t.Errorf("Necromancer pre-L15 should not summon thrall: proc=%f dmg=%d", mods.PetAttackProc, mods.PetAttackDmg)
+	}
+}
+
+func TestNecromancy_ImprovedUndeadThrallsRespectsExistingHigherProc(t *testing.T) {
+	// If a stronger pet (e.g. an adventure pet) is already in slot, don't downgrade.
+	c := &DnDCharacter{Class: ClassMage, Subclass: SubclassNecromancy, Level: 15, CON: 14}
+	mods := &CombatModifiers{DamageReduct: 1.0, PetAttackProc: 0.5, PetAttackDmg: 12}
+	applySubclassPassives(&CombatStats{}, mods, c)
+	if mods.PetAttackProc != 0.5 {
+		t.Errorf("thrall overwrote stronger PetAttackProc: got %f, want 0.5", mods.PetAttackProc)
+	}
+	if mods.PetAttackDmg != 12 {
+		t.Errorf("thrall overwrote stronger PetAttackDmg: got %d, want 12", mods.PetAttackDmg)
+	}
+}