Hundreds of tiny green flames surge forward, each clawing the air with flickering fingers. Add this CR 3 undead incorporeal ectoplasmic swarm to your next adventure to challenge your players.

The Undersea Sourcebook for Dungeons & Dragons 5e is a collection of player and GM options for running ocean-themed adventures. Subscribe for free weekly sea monsters and monthly encounters.

Over the next three weeks, we’ve got three undead creatures, two of which are themed around ectoplasm. Ectoplasm might be described as life-essence, a residue left by creatures that have crossed between the Mortal Realm and the Realm of Death. Slimer from Ghostbusters is the best example of an ectoplasmic creature from popular culture. That slime is pure ectoplasm.

Eery Ectoplasmic Swarm Fiends

Hundreds of tiny green flames surge forward, each clawing the air with flickering fingers.

Ectoplasmic swarms appear as green flames, with darker flames within that seem to function as eyes and mouths. Their shape is roughly humanoid, with legs and arms ending in flickering claws. Besides these features, they are otherwise featureless and transparent.

Necromancy is usually at the root of an ectoplasmic swarm’s appearance, though they can form wherever a large concentration of departed souls is present. Although tiny, swarms of these flamelike creatures can quickly suck the life out of the living.

Animated ectoplasm seeks to devour souls, which sustain it and gives it a collective memory drawn from all the lives it has consumed. Drawing information out of the ectoplasm, usually through a seance, is difficult because of the mob of souls present. However, if the paranormalist can bring order to the discord, the souls can provide many insights from their collective memory.

 

Remember to join our newsletter to get new D&D monsters and adventures every month.

Ectoplasmic swarms are tough to kill because they’re incorporeal and have the normal resistances of a swarm. Give your players access to holy water and a chance to figure out the swarm’s weakness, otherwise this could be a tough slog.

If you enjoyed this monster, consider buying one of our bestselling books. We appreciate the support!