The Black Hole costs 6 actions to cast, and so it expends 3 turns.  The spell conjures up a giant black hole that nothing, not even light, can escape from.  It will draw in anything within a 200 ft. radius, except the spellcaster.  So make sure your teammates are out of the way before you cast it, but make sure they can protect you.  The spell has a range of 400 ft. and an Area of Effect radius of 200 ft.  The Black hole lasts for 2 minutes.