Furnace of Rath

If a source would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Dictate of the Twin Gods

Flash
If a source would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Inquisitor's Flail

If equipped creature would deal combat damage, it deals double that damage instead.
If another creature would deal combat damage to equipped creature, it deals double that damage to equipped creature instead.
Equip {2}

Phyrexian Vindicator

Flying
If damage would be dealt to this creature, prevent that damage. When damage is prevented this way, this creature deals that much damage to any other target.

Stuffy Doll

Indestructible
As this creature enters, choose a player.
Whenever this creature is dealt damage, it deals that much damage to the chosen player.
{T}: This creature deals 1 damage to itself.

Star of Extinction

Destroy target land. Star of Extinction deals 20 damage to each creature and each planeswalker.

Jaya's Immolating Inferno

(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Jaya's Immolating Inferno deals X damage to each of up to three targets.

Brash Taunter

Indestructible
Whenever this creature is dealt damage, it deals that much damage to target opponent.
{2}{R}, {T}: This creature fights another target creature.