Ki, Who Paints her Dreams

Nightmares you control have fear.
{x}{b/g}{b/g}{t}, reveal the top X cards of your library:
put a permanent revealed this way with mana
value X or less onto the battlefield. It's a black nightmare creature in addition to its other types
with base power and toughness equal to its mana
value. Then put the cards revealed this was on the bottom of your library in a random order.