Callisar's Corpse Explosion

At 6th level, you can make up to two of your undead that you control explode. Dealing 11d8 force damage with in a 10 ft radius, if it is wearing armor add, +2 for light armor, +4 for medium armor, and +6 for heavy armor, to the damage roll as piercing damage. Creatures within this radius have to make a Dex Saving Throw, on a success they take half damage. If the creature fails, they take full damage, pushed 10 ft back, and are knock prone.

At higher levels. for each extra spell slot level, you can add one more target undead you control, and an additional 1d8 force damage to the damage roll.