Ouroboros, The Endless

Eminence: Creatures you control have "{t}, sacrifice:
add one mana of any color."
When Ouroboros, The Endless enter the battlefield
each player may sacrifice a creature, with they do
they add one mana of any color. Then put that many
sacrificed creatures in this turn +1/+0 counters on him.
When Ouroboros, The Endless leaves the battlefield
deal damage equal to his power to any target.