Yldir, The God of Bane

-3: Target permanent gets deathtouch and lifelink until end of turn.
-10: Exile 5 target creatures your opponent controls. Create 5 1/1 black Swamp Beast tokens.
-12: Exile the top 20 cards of target player's library. Destroy target permanent. Target creature your opponent control gets -5/-5 until end of turn.