Cthulhu, Titan of the Deep

When Cthulhu enters the battlefield, sacrifice it unless it escaped.

Whenever Cthulhu enters the battlefield or attacks, return target Kraken, Leviathan, Octopus, or Serpent from your graveyard. Sacrifice that creature at the beginning of the next end step.

Escape— {u}{u}{b}{b} , Exile five other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)