The Meep

Ward—Pay 3 life.
Whenever The Meep attacks, you may sacrifice another creature. If you do, creatures you control have base power and toughness X/X until end of turn, where X is the sacrificed creature's mana value.

Sol Ring

Swamp

Desolation Twin

When you cast this spell, create a 10/10 colorless Eldrazi creature token.

Reiver Demon

Flying
When Reiver Demon enters, if you cast it from your hand, destroy all nonartifact, nonblack creatures. They can't be regenerated.