Ulamog, End of all

+4: Exile Target Permanent. Add {X} to your manna pool, where X is that permanent's converted mana cost
-X: Ulamog, End of All becomes a 10/10 Legendary Creature - Eldrazi with Annihilate X, Indestructible, and Hexproof
-20: Exile all permanents target opponent controls. Then, exile all cards in that player's library except the last. That player exiles their hand.