Chaotic Nova

You’ve used this technique before, but you know you can go farther. You harness energy from within yourself taking 1d8 of damage, as you form the orb of dark energy you lift up into the air creating a 4 ft diameter sphere of chaotic energy. It pulsates with white flashes, but keeps its dark colors. As you hurl the chaotic nova at a group of enemies, the chaotic orb explodes in a 20 ft sphere. Each enemy in the 20ft sphere must make a Constitution saving throw, or take 3d12 radiant damage. On a success, enemies take half damage dealt. 

If two or more hit die land on the same number, an additional wave from your chaotic nova’s explosion can damage any creature inside the 20ft sphere for an additional 2d6 of radiant damage.

At higher levels: When you cast this spell using a spell slot higher of 4th level or higher, the damage increases by 1d12 for each slot level above 3rd.