Atraxa's Challenge

When Atraxa's Challenge enters the battlefield, distribute X +1/+1 counters among creatures you control.
Whenever a creature an opponent controls dies, choose one: Exile that creature instead; or proliferate; or each opponent loses 1 life and you gain 1 life; or create X 1/1 colorless Germ creature tokens, where X is the power of the creature that died.