D&D Monster Symbiotes
During the post-show Discord chat for today’s Wandering DMs episode, the topic of multiple monsters operating in a symbiotic state came up. It’s a delightful way of turning up the danger and excitement, so I decided to both document those ideas here and come up with some more. Of course, since I’m not a fan of using stock monsters in TTRPGs, I’d find other ways to spice these up for my own use, but I’ll stick with stock monsters for the purposes of this list in the name of general applicability (and under the assumption that other GMs who make their own monsters would be able to adapt these pairings to their own tastes based on why they go well together).
1. Corporeal Undead (Zombies, Ghouls, etc.) + Necrophagous Critters (Rot Grubs, Carrion Crawler Larvae, etc.)
Mashing together ideas about carrion crawlers laying eggs in corpses and PCs turning into zombies/ghouls was where the whole discussion started. The undead serve as a vessel to transport what would otherwise be traps-as-monsters to the PCs, and the additional threat posed by the critters ramps up the intensity of fighting the undead. Extra points for also leading to disgusting visual descriptions (though you can also get that with just normal maggots or worms as done in The Crucible of Freya, if you don’t want more danger).
2. Gelatinous Cube + Skeletons
Credit to Paul for this idea. Since bones floating in a gelatinous cube are a common telegraph for that ooze, the extra threat might be overlooked more easily by veteran players than novices, which is always a nice bonus. This can also work with any sort of ooze monster that doesn’t consume bones and any sort of bone-based monster (like a bone golem). For whatever reason, the whole idea seems somehow reminiscent of the red skeletons in classic Castlevania games even though the visual is probably more like the ectoplasm enemies in Darkest Dungeon.
3. Skeletons/Zombies + Fungus/Mold/Plant Monsters
Similar to the first one, this is about using fairly weak undead as transportation vessels for more dangerous monsters that are generally stationary (or nearly so). Skeletons with fungi growing on them is an idea that I’ve used before to good effect, and the general banter that followed with Dan and Paul as well as fellow fans Baquies and Joshua Macy brought up the other possibilities. As someone who’s a big fan of those plant-like monsters for some reason, I’m looking forward to a chance to put this to use.
4. Gargoyles + Green Slime
An idea for when you want a transportation vessel that isn't undead. Gargoyles aren’t much of a threat by default in most editions of D&D (perhaps aside from often resisting non-magical weapons), but they’re both made of stone and capable of flight. Green slime is very dangerous (particularly in pre-2000 editions of D&D), but it’s rather stationary and easily destroyed once noticed. However, green slime doesn’t affect stone, so it could hitch a ride on the gargoyles to be spread more easily while also being somewhat protected from retaliation by virtue of being out of reach. This same trick can work with other molds/oozes/plants/slimes/etc. that don’t affect stone. The gargoyles could potentially be switched for other stone monsters, but their flight is a key part of what makes them so much more dangerous when paired with green slime.
5. Grimlocks + Shadows
This is a bit of an unintuitive combination, but hear me out. Grimlocks are blind, so they’re at ease in total darkness. Shadows would be nigh-invisible without a source of light. Granted, the shadows could also feed on the grimlocks with impunity if they so desired, so magical or otherwise supernatural compulsion might be necessary to make them all work together. If you can find a way to pull it off, though, it can be a devastating combination. Pairing other incorporeal creatures with grimlocks could also work, as could other blind creatures with shadows, all depending on the specifics. Of the blind creatures that might work with the type of person who’d typically command shadows, grimlocks seemed the best general partner minion(*), but I might be overlooking something.
(*): I'm aware of skeletons, which admittedly would be a great match in settings where they don’t have conventional vision, but double-dipping on undead means too many vulnerabilities to anti-undead measures.
6. Harpies + Otyughs
Here’s an ecological pairing that also has combat synergies. Harpies are filthy creatures, and otyughs thrive in filth, so the two ought to get along great in that capacity. When it comes to fighting, otyughs can use their tentacles to hold foes in place while the harpies attack from the air. Other flying creatures can work in place of the harpies, but I feel like their filthiness works too well lore-wise with otyughs to replace them, and I have similar thoughts for replacing the otyughs with other grappling creatures (like giant crabs or ropers).
7. Petrifying Creatures (Cockatrice, Basilisk, Gorgon, etc.) + Xorn
This is another ecological pairing with combat synergies. The petrifying creatures can turn fleshy targets (like most PCs) into stone. Xorn eat stone. Thus, aside from the obvious, the xorn would threaten petrified PCs to put more pressure on the rest of the party to get them out of the encounter intact and suitable for restoration. In a bit of a twist compared to the rest of this list, the pairing might make the xorn less of a danger in combat (as they’d be distracted by the appetizing new snacks) and turn them into more of a high-stakes negotiation built into a combat situation with the petrifying creatures. This would still make the combat more dangerous by encouraging some of the PCs to turn their attention to the xorn, essentially splitting the party while still keeping them all together, and those sort of split-objective combats are often much more interesting than more straightforward affairs.