Mutanus the Devourer: how to beat

Mutanus the Devourer — dungeon “Howling Caverns”, level 21. The deck: phases, turn cycle, damage and healing by mode, cold, test strike, role tips.

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Dungeon Howling Caverns, final boss, level 21.

The boss plays its own deck: every turn it plays the next line of its phase’s cycle, with no randomness. Learn the cycle and you know what is coming. The numbers on this page are the same as in the card tooltip in combat: before Hardiness and Defender’s Stance. Mechanics in detail — Boss mechanics.

In short

Modes: Heroic (at level 60), Normal (at the place’s level, 15–21), Keystone +10 (Mythic+, at level 60).
2 phases, 7 cards in the deck. Schools: 🌿 Nature 4, 🌑 Darkness 2, 🩸 Blood 1.
“Damp and Chilly” cold: every enemy turn, everyone through shields — heroic 600, keystone +10 500 to each before Hardiness. No cold in normal mode.
“It's You, Isn't It” test strike — on boss turns 8 and 16: heroic 7,000, keystone +10 8,000; 40% weaker with a defensive card on yourself.
The heaviest hit is “It's You, Isn't It”: heroic 7,000, keystone +10 8,000.

Phases and turn cycle

The phase changes with the boss’s Health. In each phase the boss goes round its own cycle: at the end it starts again. The boss’s next turn shows on its portrait.

1. “Listening” — from the start of the fight

Down to 40%: takes someone every 4 turns.

Cycle step	What the boss plays
1	🌿 Root
2	🌿 Root + 🌿 Took You to Listen
3	🌿 Root + 🌿 Repeating
4	🌑 All the Voices at Once

2. “Speaking” — below 40% Health

Below 40%: voices on everyone, and angrier.

On entering the phase the boss plays at once: 🩸 Started Talking.

Cycle step	What the boss plays
1	🌿 Root + 🌑 Whispers to Everyone
2	🌿 Took You to Listen
3	🌿 Root + 🌿 Repeating
4	🌑 All the Voices at Once

The “It's You, Isn't It” test strike is not part of the cycle: the boss announces it on its turns 7 and 15 and hits on turns 8 and 16.

Cards and numbers

The number is what a hit takes before Hardiness (through shields — from Health only), how much the boss heals itself, the shield it puts up, a minion’s Health. A dash means the card is not in that mode or has no number. Keystone: +10 numbers; hits are the same from +7 to +9 and weaker per level below +7.

Card	What it does	Heroic	Normal	Keystone +10	How to answer
🌿 It's You, Isn't It · Nature, test strike	A test strike on whoever holds the boss’s attention (usually the tank). The boss announces it on its own, outside the cycle, and hits on its 8th and 16th turn; one turn before, there is a countdown on the portrait and a warning above your hand. The target plays a defensive card on themselves before the hit — it is 40% weaker. Not in normal mode. Through shields.	7,000 · with a defensive card 4,200	—	8,000 · with a defensive card 4,800	Test strike, one turn of warning. The tank plays a defensive card, the healer tops him up in advance.
🌿 Root · Nature, hit	A hit on whoever holds the boss’s attention (usually the tank).	2,350	400	4,100	A plain hit.
🌿 Took You to Listen · Nature, swallows a fighter	Swallows a damage dealer for 2 turns: they cannot act or be healed and take a hit through shields every turn. Take 5% of the boss’s Health and it spits them out sooner.	188 per turn	32 per turn	328 per turn	The fighter is out of the fight for 2 turns and cannot be healed. Take 5% of its Health and the forest lets go sooner.
🌿 Repeating · Nature, card freeze	Freezes 1 card(s) in the hand of a damage dealer or the healer (past the tank) for a turn.	—	—	—	One of the target's cards is locked for a turn.
🌑 All the Voices at Once · Darkness, charge	A charge: in 1 turn it hits everyone, the number is for each. Shields hold half, ignores 50% of Hardiness.	846	96	984	One turn of warning. Raise everyone's Health.
🌑 Whispers to Everyone · Darkness, damage over time	Damage over time on everyone. The number is per turn, for 3 turns. A repeat refreshes it.	176 per turn	20 per turn	205 per turn	On everyone. Party healing.
🩸 Started Talking · Blood, boss empower	The boss’s hits ×1.15 until the fight ends.	—	—	—	Stronger by 15% until the fight ends.

“Damp and Chilly” cold

Nobody has heated this place for a hundred years. The forest does not freeze, but you do.

Heroic: 600 to each per enemy turn, before Hardiness.
Keystone +10: 500 to each per enemy turn, before Hardiness.
Hits every fighter in the party through shields; Hardiness reduces it — better gear takes less.
The answer is healing every turn: shields do not stop cold. Healer cards do it best — they heal Health only.
No cold in normal mode.

Test strike

“It's You, Isn't It” — on boss turns 8 and 16, through shields, on whoever holds the boss’s attention (usually the tank). On heroic, while the party’s tank is alive, it goes to the tank. Not in normal mode.
Heroic: 7,000 before Hardiness; 4,200 if the target answered with a defensive card.
Keystone +10: 8,000 before Hardiness; 4,800 if the target answered with a defensive card.
One turn before the hit there is a countdown on the portrait and a warning above your hand. The target plays a defensive card on themselves: a self-shield, damage reduction or “cannot be killed”. A card someone else plays on the target does not count.

Enrage

Heroic: from party turn 40, every boss turn is 4% stronger, and it stacks.
Normal: as before — if the fight drags on past its expected length, the boss hits harder every turn.
Keystone +10: as before — if the fight drags on past its expected length, the boss hits harder every turn.

Roles

Tank

The “It's You, Isn't It” test strike lands on the boss’s 8th and 16th turn (heroic and keystone +10). One turn before, play a defensive card on yourself — a self-shield, damage reduction or “cannot be killed”: the hit becomes 40% weaker. Keep such a card in hand for those turns.
Shields do not stop this hit: the healer tops up your Health before it.
“Root” hits you. Keep Taunt on rhythm: while the boss hits the tank, the rest stay whole. The heaviest is “Root” (“Listening” phase, cycle step 1).
Do not fall: on heroic, mythic and in keystones, without a living tank the boss’s hits on its focus go through shields. A resident can be the tank too.

Healer

“Damp and Chilly” cold hits everyone through shields every enemy turn: heroic — 600, keystone +10 — 500 to each before Hardiness. Heal everyone every turn; healer cards do it best — they heal Health only.
“All the Voices at Once” and “Whispers to Everyone” hit everyone. Before such turns, get everyone above half Health; “All the Voices at Once” goes half through shields: shields hold half, the rest hits Health.
“Whispers to Everyone”: damage over time — outheal it; a cleanse helps.
“Started Talking”: the boss hits harder — keep crystals and heals in reserve for those turns.

Damage dealers

“Took You to Listen”: damage dealers save the swallowed one — take the required share of the boss’s Health and it spits them out sooner.
“Repeating” hits your cards and crystals: do not hoard everything for one turn.
Do not drag it out: heroic — enrage from turn 40.

The heaviest hits

“It's You, Isn't It” — test strike, through shields.
“Root” — on the tank; “Listening” phase, cycle step 1.
“All the Voices at Once” — on everyone, half through shields, ignores 50% of Hardiness; “Listening” phase, cycle step 4.

Loot

All of the boss’s loot with rough drop chances is in the item atlas; rules and items by boss are on the Howling Caverns page.

Previous boss — Naralex the Sleeping Seer.

All bosses of the place — Howling Caverns. Rules of a fight against a boss with a deck — How to beat: every boss.