Doom: "At the end of the enemy turn, if it has at least as much Doom as HP, it dies." Doom stacks and does not wear off, and it compares against HP only, so enemy Block does not protect against it.

Cards that apply Doom

Numbers are unupgraded.

CardCostRarityDoom
Blight Strike1Common8 damage, then Doom equal to the damage dealt
Negative Pulse1Common7 to all enemies, and 5 Block
Scourge1Common13, and draw 1 card
No Escape1Uncommon10, plus 5 for every 10 Doom already on the enemy
Countdown1Uncommon Power6 to a random enemy at the start of each of your turns
Deathbringer2Uncommon21 to all enemies, and 1 Weak
Oblivion0Rare3 to the enemy for every card you play this turn
End of Days3Rare29 to all enemies, then kills every enemy with at least as much Doom as HP
Reaper Form3Rare PowerYour Attacks apply Doom equal to the damage they deal

Potion of Doom applies 33 Doom.

Cards that use Doom

CardCostRarityEffect
Time's Up2RareDeal damage equal to the enemy's Doom. Exhaust
Death's Door1UncommonGain 6 Block, twice more if you applied Doom this turn
Shroud1Uncommon PowerGain 2 Block whenever you apply Doom
Sleight of Flesh2Uncommon PowerWhenever you apply a debuff to an enemy, it takes 9 damage

End of Days is the only card that kills with Doom during your own turn. Otherwise the enemy takes its turn first and dies at the end of it.

Doom on yourself

Neurosurge (0 cost, rare Power) gives 3 energy and draws 2 cards, then applies 3 Doom to you at the start of each of your turns. Doom on you works the same way: you die at the end of your turn if your Doom reaches your HP.

Enemies Doom does not finish early

Test Subject, an act 3 boss, revives twice. Doom removes it only after its second revive. See act 3 bosses.

See the Necrobinder guide for Osty, Summon and Souls.