Boss mechanics: charges, cold, test strikes, card schools

Every boss deck mechanic: what each card does, how it shows in combat and how to answer. Schools, cold, test strikes, enrage, healer cards — and who has what.

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Each of the 166 bosses has its own deck. There are many cards but few kinds — here is each kind: what it does, how it shows in combat, how to answer it, and which bosses have it. A specific boss’s numbers are on its page in How to beat.

How the boss plays

Every turn the boss plays the next line of its phase’s cycle — no randomness. Each phase has its own cycle; the phase changes with the boss’s Health, and on entering a phase the boss may play a card at once.
The next turn shows on the boss portrait, charges have a countdown; the card tooltip shows the school, what the card does and how much it takes from you.
The boss has general hit and turn caps only on normal difficulty; it has no Onslaught and no shared card pool: everything it does is in its deck.

Card schools

Every card has a school with an icon. It hints at how to answer; it is not a resistance — there is no protection against schools.

Icon	School	How to answer	Bosses	Cards
⚔	Physical	a plain hit: a defensive card and a shield	154	396
🌑	Darkness	cards, names, healing: read what is written and decide	72	188
🔥	Fire	hit and burn: shield in advance, remove the burn or outheal it	48	144
🩸	Blood	cuts the target’s healing and stacks: shields instead of healing	98	113
⛰	Earth	a heavy hit or a rockfall: shield in advance, top up the party	52	111
🌿	Nature	summons and growth: hit what was summoned	49	87
☠	Poison	damage over time and blight: outheal it, a cleanse helps	22	47
❄	Cold	a heavy hit with a warning, often through shields: raise everyone’s Health in advance	18	37
⚡	Storm	jumps around the party, punishes unspent crystals: keep everyone above half, spend everything	7	13

Cold

166 of 166 bosses have it — on heroic, mythic and in keystones. Every enemy turn it hits every fighter in the party for one number, through shields; Hardiness reduces it. No cold in normal mode.
How much is set per boss: mythic 560–1,060, heroic 320–1,200, keystone +10 320–1,000 to each before Hardiness.
In combat — the ❄ icon on the boss with “You take about N per turn”.
The answer is healing every turn; healer cards do it best — they heal Health only.

Test strike: numbers

Mythic 9,000, heroic 7,000, keystone +10 8,000 before Hardiness; 40% weaker with a defensive card on yourself. Each boss has its own turns — on its page.

All mechanics

Charge

A strong card with a countdown: the boss announces it and hits 1–2 of its turns later — the tank, everyone or a chosen target. Some charges are heals: the boss charges up and then heals itself.

How it shows in combat. The boss portrait shows “⚡ name · in N”, one turn before the hit the countdown turns red and a warning shows above your hand; the log says “prepares … fires in N turns”; when the charge fires, large text appears on the board.
How to answer. A defensive card and full Health for the hit; for a hit on everyone, get everyone above half. Some charges can be broken: take the share of the boss’s Health from the tooltip during the countdown (“Take 5% of its Health and there will be no hit”). A broken charge is sometimes replaced by another card — that is written on the card too.
Who has it (112): Oglut Flint, Bazzalan Bloodblade, Anacra the Slithering, Lady Serpenta, Cobrahn the Scaled, Naralex the Sleeping Seer, Mutanus the Devourer, Mr. Hammer and 104 more.

Test strike

Once or twice per fight — a very heavy hit on whoever holds the boss’s attention (usually the tank); on heroic, while the party’s tank is alive, on the tank. Its turns are outside the cycle and set per boss. The strength is one number for all tanks in the mode. Heroic, mythic and keystones only.

How it shows in combat. One turn before the hit there is a countdown on the portrait and a warning above your hand naming the target. Once the answer counts, the warning says “Your defensive card counts”.
How to answer. The target plays a defensive card on themselves — a self-shield, damage reduction or “cannot be killed”: the hit is 40% weaker. A card someone else plays on the target does not count. Shields usually do not stop this hit — the healer tops up the tank in advance.
Who has it (166): Oglut Flint, Taragmar the Ravenous, Jergosh the Invoker, Bazzalan Bloodblade, Anacra the Slithering, Lady Serpenta, Cobrahn the Scaled, Fangor the Scaled and 158 more.

Mark

The boss marks a fighter — usually past the tank — and a few turns later hits the marked one; some marks also catch a neighbour.

How it shows in combat. A mark icon with the card’s name on the marked fighter’s portrait; the log says “marks … in N turns”.
How to answer. Cleanse the mark (unless the card says a cleanse does not help), shield the marked fighter or top up their Health before the hit.
Who has it (11): Cobrahn the Scaled, Gromval the Igniter, Rot-Totemist Mordrek, Pyromancer Loregrain, Doctor Theolen Bloodletter, Darkmaster Gandling, Archivist Galford, Magmadar, Lava Beast and 3 more.

Hit on everyone and chain

A hit on the whole party: the number is for each. A chain jumps across several fighters, each next hit stronger. Some hits go through shields or ignore part of Hardiness — the card says so.

How it shows in combat. The card in the cycle is visible in advance on the portrait (“Next turn: …”).
How to answer. Before a turn with such a card — everyone above half Health and shields up; through shields only Health helps.
Who has it (71): Taragmar the Ravenous, Bazzalan Bloodblade, Naralex the Sleeping Seer, Gilnid the Smelter, Mr. Hammer, Edwin Keenblade, Apothecary Hummel, Abyssal Guardian Helios and 63 more.

Damage over time

Burns, poisons, bleeds: damage at the end of the turn for several turns. A repeat refreshes the duration. Stacking damage on everyone grows in stacks — each card adds a stack.

How it shows in combat. An icon on the fighter; the Health bar shows the hatched part the ticks will take; on the tank, large above the portrait — “☠ −N/turn”.
How to answer. Outheal it; a cleanse helps. Against the stacking kind — heal the whole party every turn.
Who has it (46): Jergosh the Invoker, Bazzalan Bloodblade, Lady Serpenta, Mutanus the Devourer, Gilnid the Smelter, Magister Whitewolf, Primordial Morok, Gromval the Igniter and 38 more.

Stacks and blight

Stacks: every hit cuts the target’s healing by another share, up to a limit. Blight: the target cannot be healed, or is healed less, for a few turns; sometimes the whole party.

How it shows in combat. An icon on the target with a tooltip showing how much weaker healing is right now.
How to answer. Shields instead of healing, heal in advance; for stacking hits on the tank — shields from the healer before the hit.
Who has it (26): Apothecary Hummel, Priestess Lornea, Targorr the Terrible, Bonegrinder the Smasher, Altar Guardian, Blood Avatar of the Memory Devourer, General Angerforge, Warmaster of the Black Forge, Warlord Drakkisar, Cult Commander, Rotbloom the Sporeling, Devourer of Roots and 18 more.

Minion with a task

The boss summons minions, each with a task: empowers the boss, heals it every turn, explodes if it survives, covers the boss (less damage to it) — or avenges: every one killed makes the boss stronger until the fight ends.

How it shows in combat. New enemies on the board; their Health and hit are in the tooltip; the task is written on the summon card.
How to answer. Kill empowering, healing, exploding and covering minions first (residents do so too). Leave avengers alone.
Who has it (75): Jergosh the Invoker, Fangor the Scaled, Gilnid the Smelter, Captain Rotsail, Edwin Keenblade, Magister Whitewolf, Primordial Morok, Mad Basil Thred and 67 more.

Timed shield, self-heal, guard

Timed shield: the boss shields itself for a few turns; fail to break it and the next card follows, often a hit on everyone. Self-heal: a prayer, a meal, a burned card. Guard: for a few turns the boss takes less damage.

How it shows in combat. A shield icon on the boss: “Timed shield: N absorb, K turns left”; the log says “shield N for K turns”, “Shield broken” or “Shield not broken”.
How to answer. Break the shield with the whole party before it runs out. A heal that charges up can be broken by a share of Health. On guard turns, hit the adds or hold your cards.
Who has it (52): Bazzalan Bloodblade, Lady Serpenta, Edwin Keenblade, Razice Darkclaw, Baron Silverlaine, Abyssal Guardian Helios, Primordial Morok, High Technocrat Mechagar the Renegade and 44 more.

Opening and empower

Opening: for a while the boss takes more damage — after its heavy hit or by the cycle. Empower: the boss hits harder for a few turns or until the fight ends; some stack.

How it shows in combat. An icon on the boss with the multiplier and duration.
How to answer. In an opening — all your strong cards. Before an empower, the healer needs crystals and heals in reserve.
Who has it (164): Oglut Flint, Taragmar the Ravenous, Jergosh the Invoker, Bazzalan Bloodblade, Anacra the Slithering, Lady Serpenta, Cobrahn the Scaled, Fangor the Scaled and 156 more.

Cards, crystals, stun

Discard knocks cards out of your hand, freeze locks them for a turn, burn takes crystals, stun skips a turn, buff removal strips buffs from everyone. Crystal penalty: every unspent crystal hits its owner.

How it shows in combat. A log line and an icon on the target; the crystal penalty tooltip shows the number per crystal.
How to answer. Do not hoard everything for one turn; spend all crystals before a penalty turn; apply buffs after a removal. After a stun a hero gets 2 turns of their own without a new one.
Who has it (66): Anacra the Slithering, Mutanus the Devourer, Rakk'zor the Hammerer, Captain Rotsail, Edwin Keenblade, Commander Springtail, Magister Whitewolf, Lord Kel'ris the Dark and 58 more.

Swallow

The boss swallows a fighter for a few turns: they cannot act or be healed and take a hit through shields every turn.

How it shows in combat. An icon on the swallowed fighter; the log says “swallows …”.
How to answer. Damage dealers take the share of the boss’s Health from the tooltip — and it spits them out sooner.
Who has it (11): Mutanus the Devourer, Hamhock Bloodletter, Dark Shaman Rotgouge, Ashen Executioner Dogrin (Graveyard Wing), Princess Terala, the Fallen Goddess, Chieftain of the Black Clan, Garr Bloodfall, Darkmaster Gandling, Baroness Anastari and 3 more.

Boss question

The boss asks a fighter a question: give up a card from hand until the fight ends (then everyone hits the boss harder until the turn ends) or stay silent — and take a heavy hit at the start of the enemy turn. For some bosses each card given up strengthens their hit on everyone.

How it shows in combat. A window with two buttons — “Give up a card” and “Stay silent” — and the hit on you; a question icon on the target. No answer before your turn ends counts as silence.
How to answer. Give up a cheap card when the party is hurt; stay silent when there is Health to spare. Residents and mercenaries answer by themselves.
Who has it (8): Taragmar the Ravenous, Direfang - Scarlet Pet (Library Wing), Sezz'ziz, Avatar of Sand, Blood Avatar of the Memory Devourer, High Interrogator Gerstahn, Guz'lok the Arena Master, Balnazzar the False Prophet, Onyxara, the Black Sovereign.

No tank — through shields

On heroic, mythic and in keystones, if the party has no living tank (it fell or there was none), the boss’s hits on its focus go through shields. The log says: “No living tank in the party: the hit goes through shields”. A resident tank counts as a tank.

Enrage

Mythic: from party turn 22, every boss turn is 25% stronger, and it stacks.
Heroic: from turn 40 — 8% per boss turn, in dungeons — 4%. Enrage does not make the cold stronger.
Onyxara, the Black Sovereign has its own enrage: Mythic: from party turn 28, every boss turn is 25% stronger, and it stacks. Heroic: from party turn 40, every boss turn is 8% stronger, and it stacks.
Normal mode and keystones — as before: if the fight drags on past its expected length, the boss hits harder every turn.

Healer cards

Each healer branch has three cards of its own against cold and hits through shields: they heal Health only and work in fights against creatures, not in PvP. More in Healer cards.

Mythic+ keystones

Keystone bosses play the same decks; Reinforcements and Shackles come as steps of their cycle. The Wound, Mark, Death Burst and Turmoil affixes are in Mythic+.