Apollyon, Wolf Among Sheep

Vigilance, Double Strike, Indestructible
Apollyon, Wolf Among Sheep's Power and
Toughness are equal to twice the amount of
creatures on the battlefield.
At the beginning of each of your turns all
creatures take X damage, where X is the amount of creatures on the battlefield.
{t}{3}{b}{r}: Group all creatures into pairs of your choice, each creature fights the other creature in
its pair, creatures killed this way are exiled