Livalina, Deity of Nyx

Indestructible Hexproof Lifelink Fear
As long as your devotion to black is less than 7, Livalina isn't a creature
Whenever you tap a swamp for mana add {b}{b} to your mana pool
{b}{b}{b}{7}{t} Take an extra turn after this one. Livalina doesn't untap during extra turns.