Bane Of The Undead

You hold in your hand the skull of an undead creature you vanquished, and with the same rage you ended it with you summon forth a wave of light to vanquish the creatures of the dark. 

As the eyes of the skull glow you target any undead creature you wish within a 50 ft sphere and force them to make a dexterity saving throw. On a failed throw they take 5d 12 fire damage and half as much on successful one. If an undead creature is killed my this spell, their body explodes making it impossible to be raised again and every creature within 5 feet of where that undead creature must make a dexterity saving throw and on a failed save they take 5d 10 fire damage and are blinded until their next turn.