Kyran, Wary Wanderer

Defender
When Kyran, Wary Wanderer enters the battlefield, an opponent gains control of it.
Whenever Kyran dies, if it was dealt damage by a creature its owner controls, its owner searches their library for a Leviathan, Shark, Kraken, Fish, Octopus, Whale, or Serpent creature, puts it onto the battlefield, then shuffles their library.