Drowning Patron

Whenever a non-token creature you control
enters or leaves the battlefield, you may pay {2}. If you do, return target creature from your graveyard to your hand that hasn't entered the graveyard this turn.
{1}{u}{b}, {t}: Target player mills 3 cards.
All they had to do was travel a bit deeper and they'd
find out what's been causing all the disappearances.