Mountain

Burn from Within

Burn from Within deals X damage to any target. If a creature is dealt damage this way, it loses indestructible until end of turn. If that creature would die this turn, exile it instead.

Banefire

Banefire deals X damage to any target.
If X is 5 or more, this spell can't be countered and the damage can't be prevented.

Bonfire of the Damned

Bonfire of the Damned deals X damage to target player or planeswalker and each creature that player or that planeswalker's controller controls.
Miracle {X}{R} (You may cast this card for its miracle cost when you draw it if it's the first card you drew this turn.)

Disintegrate

Disintegrate deals X damage to any target. If it's a creature, it can't be regenerated this turn, and if it would die this turn, exile it instead.

Heartless Hidetsugu

{T}: Heartless Hidetsugu deals damage to each player equal to half that player's life total, rounded down.

Earthquake

Earthquake deals X damage to each creature without flying and each player.

By Force

Blaze

Meteor Shower

Meteor Shower deals X plus 1 damage divided as you choose among any number of targets.

Fireball

This spell costs {1} more to cast for each target beyond the first.
Fireball deals X damage divided evenly, rounded down, among any number of targets.

Lava Burst

Lava Burst deals X damage to any target. If Lava Burst would deal damage to a creature, that damage can't be prevented or dealt instead to another permanent or player.