Magik

When Magik enters the battlefield, put a 2/2 black Demon creature token onto the battlefield under your control.
{w/b}: Magik gets +1/+1 until end of turn.
{w/b}{w/b}: Demons you control get +1/+1 until end of turn.
{w/b}{w/b}{w/b}: Exile Magik, then return her to the battlefield under your control.