Blackout

when a creature within range cast a spell you can consume the spell in Darkness as a reaction. if the spell is 4th level or lower it is consumed and the casting is interrupted. if the spell is 5th level or higher, then you can either delay the spell for a round or turn this spell into a concentration spell, and while concentrating on this spell the spell that you consumed in darkness is delayed until you break concentration, when you break concentration the delayed spell is instantly cast. if you maintain concentration on this spell till the end of the duration the consumed spell is interrupted. you can concentration on this spell as many rounds as the spell level consumed.