Blackened Heart

Adapated from Genuine Fantasy Press

Level 3 Necromancy

(Cleric, Druid, Sorcerer, Wizard)
Casting Time: Action
Range: 60 feet
Components: V, S
Duration: Instantaneous
You reach out towards a creature that you can see. The target must succeed a Constitution saving throw or take 10d6 Poison damage at the start of its next turn, as its body becomes filled with vile poison. This spell has no effect on Constructs or Undead.
If the target is reduced to 0 Hit Points before the start of its next turn, the poison within them explodes outward in a shower of disgusting bile. Each other creature within a 10-foot Sphere of the target must make a Dexterity saving throw. A creature takes 10d6 Poison damage on a failed save, or half as much on a successful one.
Using a Higher-Level Spell Slot. The damage increases by 1d6 for each Spell Slot level above 3.