When you cast this spell, you target an undead under your control within 60 feet the target is imbued with a volatile magical energy for the duration (equal to your INT modifier). Choose one of the following effects when casting the spell: (Only one creature can be imbued at a time)
Manual Detonation:
At any point within the spells duration you can use a bonus action to activate the magical energies causing the creature it was cast upon to explode each creature in a 10ft radius must make a Constitution Saving throw. A target takes 4D6 necrotic damage on a failed save and half as much on a success.
Triggered Detonation
When casting the spell you set a trigger which if it occurs activates the explosion. The trigger must be a set of instructions the undead is able to execute.
Examples include: "When the undead grapples another creature." "When a certain number of creatures get within the blast radius." "Someone attacks the undead."
At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the damage increases by 2d6 for every 2 levels above 4th. Alternatively can add 5 ft to the radius for every 2 levels above 4th. Can also detonate 1 additional target for every 2 levels above 4th.
* - (A Medium or smaller undead under the control of the caster, which the spell consumes. (If detonated) )