Teras, Wraith of Souls

Reap {w}{b}{b} ({w}{b}{b}, You may exile target creature in your graveyard, then gain life equal to that creature's toughness.)
Whenever you reap a creature Teras, Wraith of Souls gets +X/+X until end of turn where X is the reaped creature's power.
Whenever you reap a creature create a 1/1 white spirit creature token with flying.