Walking Bomb

You reach out and imbue the living essence of a creature with an incendiary magical force.

Select a creature within range and that creature becomes enveloped with necrotic energy. If this creature is reduced to zero hit points before the spell ends, the energy bursts out of it in an explosion of necrotic energy. All creatures within a 20 foot radius sphere centered on the creature must make a constitution saving throw, taking 4d10 necrotic damage on a failure or half as much on a success.

Additionally, if the explosion reduces another creature to 0 hit points, you can cause a secondary explosion to erupt from this creature. All creatures within a 15 foot radius of the secondary creature must repeat the constitution saving throw, taking 3d10 damage on a failure or half as much on a success.

At higher levels: Whenever you cast this spell using a spell slot of 6th level or higher, the spell's damage increases by 1d10 for every two spell levels above 5th.

Additionally, for every spell level above 5th, you can create one subsequent explosion every time an explosion reduces another creature to 0 hit points. Each time you do so, the explosion deals 1d10 less damage within a spherical range with a radius 5 feet smaller than the previous explosion, to a minimum of 1d10 damage in a 5 foot radius.