Sharkshaw III, Sahuagin Heir

Sharkshaw III has nightbound as long as you
control five or fewer Sharks.
At the beginning of each upkeep, if you've
completed a dungeon, create a 3/3 blue Shark
Warrior creature token with vigilance. Otherwise,
venture into the dungeon.
At the beginning of your end step, gain control
of all Sharks your opponents control.