Walking Bomb

 When you cast this spell, choose a creature within as a bolt of purplish necrotic latches onto them, forcing a Constitution saving throw. On a failed save the creature is cursed. While cursed in this way the creature takes 6d6 necrotic damage at the start of each of its turns.

If the creature dies while the spell is still in effect, they detonate in a 20-foot radius sphere, forcing a Dexterity saving throw for any creature in the area. On a failed save they take 14d6 necrotic damage, or half as much on a save.