Eternal sea

Indestructible
At the beginning of your end step, add a charge counter to this.
When the number of charge counters on eternal
sea is a prime number, return a creature card
from a graveyard to the battlefield.
When the number of charge counters on eternal
sea is odd, you gain an extra turn after this one.
When the number of charge counters on eternal
sea is even, gain control of target permanent an opponent controls.