Death by Dragons

When Death by Dragons enters the battlefield, each opponent sacrifices X creatures. When a creature enters the battlefield under your control, it gets +2 +2 and haste until end of turn, and you lose X life, where X is the creature's converted mana cost.
{x}{p/r}{ut}: Return X creatures with converted mana cost equal to the amount of life you lost this turn plus 1 from a graveyard to the battlefield. You lose 5 life.