Imminent Doom

Imminent Doom enters with a doom counter on it.
Whenever you cast a spell with mana value equal to the number of doom counters on Imminent Doom, Imminent Doom deals that much damage to any target. Then put a doom counter on Imminent Doom.

Amonkhet Remastered

Imminent Doom enters the battlefield with a doom counter on it.
Whenever you cast a spell with converted mana cost equal to the number of doom counters on Imminent Doom, Imminent Doom deals that much damage to any target. Then put a doom counter on Imminent Doom.

Hour of Devastation

Imminent Doom enters the battlefield with a doom counter on it.
Whenever you cast a spell with converted mana cost equal to the number of doom counters on Imminent Doom, Imminent Doom deals that much damage to target creature or player. Then put a doom counter on Imminent Doom.

Hour of Devastation Promos

If a spell has {X} in its mana cost, include the value chosen for that X when determining the mana value of that spell.

Imminent Doom's triggered ability resolves before the spell that caused it to trigger. The ability will resolve even if that spell is countered.

The amount of damage Imminent Doom's triggered ability deals is the number of counters it had on it as the ability triggered. For example, if you cast Shock and then respond to Imminent Doom's triggered ability with a second Shock, both abilities cause Imminent Doom to deal 1 damage and Imminent Doom will end up with three doom counters on it.