Volturnos, King of the Deep

Flying
Forgotten Nightmares - Volturnos has hexproof
as long as you control at least one other creature.
Volturnos enters the battlefield with 3 Tides of
Death counters on it. At the beginning of combat
on your turn, remove one. When you remove
the last one, creatures you control gain flying and
doublestrike until end of turn. Then put 3 Tides
of Death counters on Volturnos.