How to Beat Ketheric Thorm in Baldur's Gate 3
A Baldur's Gate 3 boss guide for Ketheric Thorm covering all three phases, the Mind Flayer Colony, Myrkul, and the party setup that makes the fight trivial.
How to Beat Ketheric Thorm in Baldur’s Gate 3
Ketheric Thorm is the Act 2 boss and one of the toughest fights in Baldur’s Gate 3 because he revives unless you break his link to the Nightsong. This guide walks the three phases and the setup that makes it manageable.
Phase 1: Rooftop
Ketheric starts on the towers rooftop with his daughters (Meli and the sentient weapon). He cannot die permanently here.
- Focus fire him to drop his HP and trigger the cutscene.
- Use Counterspell when he casts big spells.
- Don’t waste resources killing the daughters — they respawn; just control them.
Phase 2: Mind Flayer Colony
After the rooftop, you descend to the colony below. Here you learn the Nightsong is his lifeline. If you spared the Nightsong in Act 2, Ketheric loses his immortality now.
- Free the Nightsong (if not already) to strip his revive.
- Without the link, Phase 2 is a straight DPS race.
Phase 3: Myrkul
Ketheric fuses with Myrkul (God of Death) for the final phase.
- Use the glowing pillars — destroying them weakens Myrkul and stops his strongest attacks.
- AoE control (Wall of Fire, Cloud of Daggers) on the narrow bridge.
- Focus the avatar; ignore the adds unless they overwhelm you.
Recommended Party
- Tank (Fighter/Paladin) to hold the bridge.
- Caster with Counterspell + Fireball.
- Healer (Life Cleric or Shadowheart) for revival and Bless.
- Rogue/Ranger for consistent single-target damage.
Final Tips
The single biggest lever is the Nightsong decision — spare her in Act 2 and this fight drops a full difficulty tier. Bring Freedom of Movement or Blindness immunity; Myrkul’s control effects punish unprotected parties.