The Thing Who Worships

When this card enters the battlefield, it becomes night.
Everytime a oponent cast a spell that will turn
night into day, negate that spell unless the oponent
sacrifice a creature.
{t}{b}{b}{b} - Sacrifice a creature, it becomes night.
All creatures with nightbound you control gets
+1/+1 and have Indestructible until the end of
this turn.