Riptide Shapeshifter

{2}{U}{U}, Sacrifice this creature: Choose a creature type. Reveal cards from the top of your library until you reveal a creature card of that type. Put that card onto the battlefield and shuffle the rest into your library.

Steal Enchantment

Enchant enchantment
You control enchanted enchantment.

Worthy Cause

Buyback {2} (You may pay an additional {2} as you cast this spell. If you do, put this card into your hand as it resolves.)
As an additional cost to cast this spell, sacrifice a creature.
You gain life equal to the sacrificed creature's toughness.

Whiteout

All creatures lose flying until end of turn.
Sacrifice a snow land: Return this card from your graveyard to your hand.