Benthor, Oceanic Tyrant

When Benthor, Oceanic Tyrant enters the battlefield, mill a card for each Island and each
Swamp you control.
Whenever Benthor attacks, you may return
target deep creature card from your graveyard to
the battlefield tapped. Sacrifice it when Benthor
leaves the battlefield. (Krakens, Leviathans,
Octopi, Serpents and Whales are deep.)
The king of the seas will stop at nothing to have his vengeance.