Kalista Gwin, One with the Sea

Whenever Kalista Gwin attacks, you may put a
Kraken, Leviathan, Octopus, or Serpent creature
card from your hand onto the battlefield tapped
and attacking. Return that creature to your hand
at end of combat.
When Kalista Gwin dies, Kraken, Leviathan,
Octopus, and Serpent creatures you control gain anchored. (This creature can't be exiled, returned to
its owner's hand, or put into its owner's library from
the battlefield.)