Walking Bomb

You send a bloated mass of rotten decay. Make a ranged spell attack against a creature within 60ft. On a hit the creature takes 2d10 necrotic damage at the start of their turns for 1 minute. If the target reaches 0 hit points it explodes a necrotic ichor....dealing 10d6 necrotic damage to all nearby creatures in a 20ft radius. When this happens the creatures caught in the blast must make a constitution saving throw against your spell save DC. On a failure they are affected as though the spell was cast upon them. On a success they are unaffected. If this explosion were to kill the creature. Then subsequent explosions do not trigger from the corpse. The effect of this spell may be removed by Dispel magic or Remove Curse.

At higher levels: For every 2 levels above 4th, the damage increases by 2d10 and the explosion increases by 2d6.