Elmyra, Seeker of the Deep

When Elmyra, Seeker of the Deep enters the battlefield, create Umbra, Loyal Companion, a legendary 4/4 blue Leviathan creature token with islandwalk.
Whenever a Leviathan you control attacks,
defending player puts the top seven cards of
their library into their graveyard.
_________________________________________
"Time to sink or swim."