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.

Taiga

Sliver creatures you control have "Whenever this creature is dealt damage, it deals that much damage to target player or planeswalker."

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

Sliver creatures you control have "{T}: Add one mana of any color."

({T}: Add {R} or {G}.)
As Stomping Ground enters, you may pay 2 life. If you don't, it enters tapped.

{T}, Pay 1 life, Sacrifice Wooded Foothills: Search your library for a Mountain or Forest card, put it onto the battlefield, then shuffle.

Search your library for a creature card, reveal it, then shuffle and put the card on top.

Any player may have Browbeat deal 5 damage to them. If no one does, target player draws three cards.

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

{T}, Pay 1 life, Sacrifice Arid Mesa: Search your library for a Mountain or Plains card, put it onto the battlefield, then shuffle.

All Slivers have "{T}: Add one mana of any color."

Whenever a player taps a land for mana, Manabarbs deals 1 damage to that player.