Monster synergy. It’s something you do not hear all that much. Surely we all know that different goblinoids will work together, or that some creatures like Ettins and Ogres will work for others for the right bribe. However, when it comes to some, they are generally overlooked except in the most obvious cases. We have seen lesser animated undead like Skeletons or Zombies work with each other or the creature that animated them – but not with something equally mindless.
Way back when I first started playing D&D, what are considered “Dungeon Hazards” were considered monsters. Green Slime, Yellow Mold, and other colony-based micro organisms were part of the Monster Manual and added to “Wandering Monsters” in that you could stumble into a growth of them while walking about. Organisms like these can prove deadly, but lack the ability to move on their own. That doesn’t prevent them from growing on something that could be a viable host and not be affected by the nature of the fungus or algae. It is entirely plausible that Zombies could be overgrown with Yellow Mold, just as Volo’s has re-introduced Russet Mold and its life cycle.
The trick would be explaining and delivering this encounter in a way that would be both unpredictable and believable.
Suggested level: 2+ (Scalable by adding more Zombies)
Description: Entering this large, circular chamber, you are immediately struck by the beam of what may be sunlight shining straight down from the center of the apex of the domed roof. It’s beautiful and haunting light showcases the central feature of the room – a circular dais at least eight feet tall. The bottom of this feature must be at least 10 feet in diameter, getting progressively smaller on each of its four steps to support an ornately carved chair or throne above the floor. Upon it sits a lone figure, gaunt and skeletal – its mouth agape with its head tilted to one side.
Its empty eye holes stare at you while something shiny in its forehead glints and sparkles in the light. The smell of mildew hangs heavy and sour in the air. The darkness of the surrounding chamber possesses highlights of a faint yellow in spots around the outer regions which might be faded mosaics, subterranean fungi, or maybe even the remains of grime-covered gilding. One cannot say for sure in the darkness.
In reality, there’s a story unfolding before the players without their knowledge. The dias itself is ornately carved with tiny figures of humanoids in gaunt and skeletal form holding up the step above them. These figures (Religion or Investigation, DC: 15) represent worshipers of Orcus. The figure atop the dias is the remains of a former Wight. One could arrive at this discovery only thorough a successful Intelligence/Arcana, Intelligence/Religion or Intelligence/Investigation DC:15 check. Its forehead is still pierced by the silvered dagger that killed it. The figure is still adorned by the tattered remains of rusted metal armor and ruined weapons it once wore. Aside form the silvered dagger, the former Wight possesses nothing of value.
Stationed equidistant around the outside of the room against the wall in the dim light are 8 Zombie servants. These servants are in tattered and destroyed ceremonial garb of an ancient religion. The moisture and darkness have allowed spores of yellow mold, likely carried from other regions in the dungeon, to flourish. Now each Zombie servitor is covered in these deadly fungal spores. The yellowish patches they are standing in are temporarily inert, having already covered the Zombies themselves in the deadly spores, but the patches that cover these undead are still active and capable of delivering their deadly burst.
As the characters enter the room, the undead will remain motionless. They will activate if attacked, approached, or if any character approaches the dais. The Zombies will behave as normal, with the following exception: The first time any Zombie is struck with a weapon, the Yellow Mold colony growing on it will burst spores in a 10-foot diameter sphere. Those caught in a burst will require a Constitution (DC: 15) saving throw or take 2d10 Poison damage and become Poisoned for 1 minute.
While poisoned this way, the Poisoned target will take a further 1d10 Poison damage at the start of each of its turns. However, a Poisoned target can roll another Constitution saving throw at the end of each of its turns. A successful save ends the condition.
A character can choose to retreat to the dias or remain on the dais when attacked. Should any character be attacked in melee by a Zombie while on the dais, the sunlight will both kill a Yellow Mold patch on a Zombie while it’s in the sunlight and neutralize any spores burst into it. The sunlight does not end a Poisoned condition nor stop or reduce an already infected character, as the spores are now internal.
Monsters: Zombies (8) – As per Monster manual, page 316
Yellow Mold (8 patches, one on each Zombie) – DMG, page 105
Treasure: None, save one Silvered Dagger
Complications: The greatest danger is if a character gets hit by multiple bursts of Yellow Mold at once. The damage can really add up in a hurry. If the DM is truly concerned about how much damage overlay might occur, then the DM can feel free to reduce the number of infected Zombies. Note, of course, that the Zombies are immune to both Poison and the Poisoned conditions, so the Yellow Mold has no effect on them. The encounter could be further down-scaled by changing the Zombies to Skeletons, or upgraded by applying the Zombie template to a larger monster or even use Zombie Ogres. Use care when considering up or down scaling.