So, I grew up playing a ton of Diablo II. 3 didn’t hit for me, and 1 wasn’t my jam, but man Diablo II had a ton of hours. My favorite class was the Necromancer, with its weird head in a bag implement, with a billion zombies running all over. My favorite thing about the class was the spell Corpse Explosion, and I don’t think I’m alone. It’s weird to me that we never got official rules for one, outside of that flash in the pan Diablo d20 conversion. So, I went ahead and wrote versions of the spell for 3, 4, and 5e D&D.

Corpse Explosion Spell
Each editions version of the spell is a little different. The 3e one has potential to hit big, and has some of the complexity of the other 3e spells and abilities. 4e’s can actually be used to explode a living minion and wipe out a horde of them. 5e’s is designed to be spammed at will, for a true Diablo II experience.
3e
Corpse Explosion
Necromancy
Level: Cleric 1, Sor/Wiz 1
Components: V, S
Casting Time: 1 Standard Action
Range: Close
Duration: Instantaneous
Target: One Corpse. (animated undead excluded)
Saving Throw: Reflex for half, see text
SR: No
Target corpse within range explodes. This deals 1d4 negative energy damage per HD the corpse possessed in life, minimum 1, maximum equal to your caster level to each creature within 5ft of the corpse.
This corpse can no longer be used as a component for the creation of undead, or resurrection spells.
4e
Corpse Explosion
Wizard Attack 1
At Will. Arcane, Necrotic, Implement
Standard Action Ranged 10
Target: Each enemy adjacent to target corpse.
Attack: Intelligence vs Reflex
Hit: 1d8+Int mod damage to each creature adjacent to target corpse.
Special: This spell can be used on living minions. If it does, the minion explodes without the need for an attack roll.
5e
Corpse Explosion
Necromancy Cantrip
Casting Time: 1 Action
Range: 120ft
Component: V, S
Duration: Instantaneous
A black strand of energy bolts from your hand, arcing into a slain creature causing its corpse to explode. Each adjacent creature takes 1d8 damage, dexterity save for half. This spells damage increases by 1d8 when you reach 5th, 11th, and 17th level to 4d8.