Moriam, Nature's Cruelty

Whenever another creature enters the battlefield under your control, you may sacrifice it. If you do, add {u}{b}{g} to your mana pool.
{x}{u}{b}{g}, {t}: Choose one - Scry X, then draw a card; or target creature gets -X/-X until end of turn; or create an X/X green Treefolk creature token with trample.
Life's vitality makes death a necessity.