I own two books describing Dungeons and Dragons green slime: the Monstrous Manual for 2nd Edition and the Dungeon Master's Guide for 3.5. In both, green slime sticks to a ceiling until, upon detecting prey, it drops on and consumes said prey, potentially turning it into more green slime.

However, both sources describe green slime as immobile. So how does green slime get on that ceiling in the first place?

The sources vaguely mention green slime grows back from spores even after it's been burned away, but what happens to a green slime glob that's already dropped? Does it just stay on the floor, eventually starving? (I assume no sane creature would step on it.)


Is there an official or unofficial ecology of green slime (from any D&D edition) that explains the green slime life cycle, justifies its feeding habits, and expands upon its typical behaviour? Particularly, how does "A glob of green slime drops on prey and turns it into green slime" lead to more green slime on the ceiling?


2 Answers 2


This answer is not RAW, but RAW probably does not answer your question.

In the real world, slime mold moves, but very slowly. With regard to combat, they are functionally immobile. With regard to life cycle, it's entirely possible they could climb back up to the ceiling in a few hours.

Alternatively, it could be part of its life cycle. Green slime may need to consume an animal in order to reproduce. They collapse onto an animal, kill it, then use the abundant nutrients to form fruiting bodies. These release spores into the air, which attach to the walls and ceiling and form more green slime. The slime on the ground dies, its purpose fulfilled. You can basically think about salmon swimming upstream, spawning, then dying, except instead of a stream, it's a person.

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    \$\begingroup\$ Because, generally speaking, the mating patterns of mold aren't published in gaming books. It's possible that there's a book out there somewhere that does, it just isn't likely. \$\endgroup\$
    – Azuaron
    Commented Aug 15, 2016 at 19:09
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    \$\begingroup\$ TSR really missed the boat on the whole Complete Fungi, Molds, and Slimes Handbook for AD&D2E, didn't they? Probably could've sold 4 or maybe even 5 copies. More seriously, the Dragondex—a pretty darn comprehensive index of print Dragon magazine articles—doesn't have a green slime entry, and the slime entries don't seem particularly informative . \$\endgroup\$ Commented Aug 15, 2016 at 19:58
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    \$\begingroup\$ @HeyICanChan Dragon 132 has one green slime entry. How to use it as a trap. Cannot find a slime "Ecology of" Article so far ... are oozes really that interesting? \$\endgroup\$ Commented Aug 15, 2016 at 20:53
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    \$\begingroup\$ +1 This is the kind of quality content I come to this website for. I expected a frame challenge along the lines of "it's a plot hole; the designers didn't think about it, and neither should you." Instead you've risen to the challenge with the requested verisimilitude - "speed 0 by combat standards doesn't mean literally immobile" is something I wouldn't have thought of, but I'll definitely need to find a way to incorporate that into my campaign now. \$\endgroup\$ Commented Aug 16, 2016 at 3:25
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    \$\begingroup\$ Your first suggestion is RAW in Astonishing Swordsmen & Sorcerers of Hyperborea (a 1eAD&D-based neoclone): "N.B.: These creatures are listed with movement 0 but in fact they can move about 12 inches per day, positioning themselves advantageously." \$\endgroup\$ Commented Aug 16, 2016 at 11:13

Green Slime: It's as much a trap as a monster

What happens to it? Nothing, really, beyond its interaction with players and their equipment. That is its purpose in the multiverse. (Aside: I expect that a great deal of green slime ends up getting burned off once the players overcome the initial reaction / damage).

How did the green slime get up there? It happened off screen, because it moves so slowly that in game / combat / melee, its speed is close enough to 0 to be 0 for purposes of melee combat.

As you ask about any edition of the game, green slime didn't begin as a monster so much as a trap or a hazard. It was something a DM placed in a dungeon as a hazard or a trap for the unwary adventuring party in an underground / dungeon / cavern setting. The following illustration has a legend describing green slime as "neutral" and "hazard." (The picture originally appeared in the AD&D 1e monster manual, and IIRC the Holmes D&D basic book circa 1977).

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Green slime in the Original Dungeons and Dragons game, was a mindless dungeon hazard

GREEN SLIME: A non-mobile hazard, Green Slime can be killed by fire or cold, but it is not affected by lightening bolts or striking by weapons. It eats away wood and metal but not stone. Green Slime sticks to flesh and penetrates it in one turn, thereafter turning the flesh into Green Slime. Green Slime cannot be scraped off, so when it contacts something the item must be discarded or excised in some way. A Cure Disease spell will also serve to kill and remove Green Slime, even when it is contact with flesh. (Monsters and Treasure p. 20; TSR, Gygax and Arneson, 1974)

How much it isn't a monster like other monsters is verified by the Monsters Reference Table (p. 4 M&T): Monster Type (NA) / Number Appearing (NA) / Armor Class (NA) / Move (nil) / Hit Dice (2) / % in Lair (Nil) / Amount & Type of Treasure (Nil)

Most monsters have a value in all of those columns, other than Ochre Jellies and Yellow Molds and such, which like Green Slime are biohazards.

Moving to AD&D 1e, green slime is mostly the same but was still listed as having 0 attacks. The text has been amplified:

Green slimes are strange plant growths found in subterranean places[...]They are sensitive to vibrations and will often drop upon passing creatures from above[...]Occasionally huge slimes or colonies of dozens have been reported. (AD&D 1e MM, p. 49)

In a discussion at the dragonsfoot AD&D 1e forums, the point was that traps (of which green slime was a kind, since it just sat there waiting to drop on the unwary) were as much a test of player skill/awareness as of character ability. The feeling of fear and the dread of dungeons wasn't just because monsters were down there. The underworld was a very dangerous place all by itself. Green slimes were one way to create fear and paranoia in a party of adventurers.

I can find no record of Ed Greenwood ever doing an "ecology of" article on the Green Slime. (It's just not that interesting of a monster). Below is an excerpt from Dragon Magazine regarding green slime and traps.

With All the Trappings
A handy guide to trap design and psychology
(by Gregg Sharp, Dragon 132, p. 28)
Active traps usually come in three basic types: biological, mechanical, and magical. Biological traps use animals or plants as a vital part of their mechanisms. For example, a biological trap may use a green slime positioned above the trip mechanism so that the slime is dislodged and falls on those passing beneath. {snip}

Previous lore has carried forward pretty consistently across editions. D&D 5e has moved green slime out of the MM and into the DMG as one of the choices for a trap. All said and done, green slime is just yucky, except that it's very dangerous to characters and their equipment.

@Dave Sherohman provided this usable-at-the-table insight, if you are interested in OSRIC or AD&D 1e compatible sources:

Astonishing Swordsmen & Sorcerers of Hyperborea has an entry for green slimes that includes the following:

  • These creatures are listed with movement 0 but in fact they can move about 12 inches per day, positioning themselves advantageously."
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    \$\begingroup\$ Note that Green Slime is not only a trap, it is not even a very good trap. It will catch you once (and probably kill you without giving you a chance or a choice), and then never again, since every party after that first one will always say "we look at the ceiling" when they enter a new room. \$\endgroup\$
    – GreySage
    Commented Aug 15, 2016 at 20:46
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    \$\begingroup\$ @GreySage The second time a green slime can kill you is if you fall into a pit trap and there's a green slime sitting there at the bottom ... \$\endgroup\$ Commented Aug 15, 2016 at 20:56
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    \$\begingroup\$ I understand that the slime somehow appeared up there off-screen; what I'd like to know is how. I want to understand how my world works on its own, even without PC interactions. \$\endgroup\$ Commented Aug 15, 2016 at 21:24
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    \$\begingroup\$ You are the God of your world. You decide how it gets there. Game books don't have to be that granular. (AD&D 2e maintained a lot of the old DM ruling ideas from 1e). How fast do you want it to go? One inch per hour? Half a foot per hour? A yard per day? In what scenario does that level of detail matter? Party is alert, avoids a GS dropping. They go dungeon delving for a day. On their way out, they pass through the same area. Has the slime been able to ascend to its perch again? The answer is: if you want it to. Think of it as a trap, if that makes more sense to you. \$\endgroup\$ Commented Aug 15, 2016 at 21:51
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    \$\begingroup\$ @Angew In D&D 3.5 the feat Initiate of Ghaunadaur (Champions of Ruin 23) grants a cleric of That Which Lurks the 5th-level Clr spell slime hurl [conj] (CR 35), which creates instantaneously three globs of green slime. In other words, in at least one edition for one setting, an explanation may be that, instead of the traditional wizard, a cleric did it. \$\endgroup\$ Commented Aug 15, 2016 at 22:43

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