Kor-Viliath, World's Lord

: Creatures you control have Swampwalk. If this card were to be exiled, send it to your graveyard instead.
X: Sacrifice target permanent. X is equal to that permanent's converted mana cost. If the permanent was a god or Dragon, add 3 to X.
-15: You get an emblem with "All lands are swamps in addition to their other types. Spells your opponents cast cost 4 more to play.