This, by the way, is also what the
formless spawn of Azoth looks like when it's wandering around a
vertical dungeon and refusing to fall apart like a proper liquid would. Only black. And here's Telecanter's
tumbling dungeon.
...there are moments in that movie where it really looks like some spirit or shroud of a ghost rising to wreak its terrible vengeance, and moments when it looks exactly like a liquid, and moments when its sharply cut edges are spooky all by themselves.
So thinking about Telecanter's
hall of four spheres*** it occurs to me that the Indiana Jones billiard ball is not the only hazard that could be flopping aimlessly around an unstable dungeon surface. And checking back on the
old Gel Cube I find I like it more than I remember. I'd always thought of it as (a) a stupid trick by a bored DM and (b) a simple herding device for a recalcitrant party. But what if you're investigating the lair of the mad alchemist or wizard? Isn't this exactly the sort of experiment you'd half expect to find? And what if the party are sleeping or resting or incapacitated in the dungeon by other threats? Isn't this just the kind of thing to make them wish they were more alert?**** Why do folks love the
Shoggoth and hate the Cube?
So how could this elderly trainwreck of a monster provide some additional fun? First I'd say make it hard to burn, and have it do damage to armor first - that'd give even your recently paralysed MU one round of clothing protection before he's Cubefood. Mechanically, I'd say the Cube doesn't get stuck if the corridor's a bit too small: it's deformable enough that if there's a hole under it that's more than, say, 70% of its area, it will slowly sink into it, and keep sinking until it finds a new cubic space to occupy.* Then:
1. What if it were averse to something - salt, say? Or attracted to catnip or fresh meat? Then the PCs could herd it around the dungeon themselves. But it won't go through closed doors - it doesn't feel a gap. And if it comes to the end of a corridor it'll reverse. Long-term dungeon inhabitants will know all these tricks, of course.
2. See how it doesn't digest dungeon walls? Clearly there's some list of what's digestible. Clearly you could carry offcuts in indigestible flasks or larger containers and use them as... artillery ammo? Because it won't splash but it's a pain to get rid of once it's in your granary/breastplate/stable. And I don't see why you shouldn't be able to snip bits off it - the mechanics for "defeating" it are vague about just what that means. I'd allow cutting weapons to sever it, thereby turning one big hazard into lots of smaller ones.
3. Alchemists are always "digesting" stuff in their flasks. Now it's a treasure/McGuffin: go get me some Gel. And like Spawn up there, it doesn't want to be used, so you'll have to chase it around the dungeon once it's realised it shouldn't be chasing you. And it can knock stuff over and close doors and slip down cracks and into the sewer system. And it can swallow all the keys, even if it can't use them.
4. because "mindless" just isn't fun. It should have some sort of intelligence, just an entirely alien one. It should know enough that it could find a lair, sneak out at night and paralyse/digest a couple of cows or children, and then disappear by morning. So you start finding these bleaching skeletons around the place and frightened villagers but no explanation. And if it's not water-based but something else altogether then it might show up in deserts or volcanoes or as the unintended consequence of universe-rending dimensional gates and passwalls.
5. Of course if it is water based it might be able to alter its size/viscosity in water. Drinking water. Which gives me an idea for displacement puzzles - do you have to float a boat/platform/statue, flood an area, swim up somewhere? Get the Cube into the water column and see how much taller it gets (I'll spare you all my computer adventure game type weight-on-a-seesaw, catapult, airlock, hydraulic and wobbly floor puzzles. You get it). With the right breadcrumb trail and an indigestible howdah you could enlist it to carry stuff out of the dungeon for you.
6. Or like an anemone it could adopt a different shape in water. And/or like a nudibranch it could
swim surprisingly efficiently, turning a slow, lumbering land threat into a serious (magical) lake guardian.
7. What if it could communicate, like Thumper, by slapping on the ground, sending booming waves of shock around the dungeon? Who/what would it call? What if it could break through thin sections of wall/floor or crumbling stone bridges?
8. What if it's one form of
the last "stone" left over from constructing the sky and therefore theologically highly important? What if you could compress it into an ooze golem? What if it brought you stuff - clues - to lead you around the dungeon to the cheese, and eventually enticed you into the mindswap device, the same trick its current mind fell for many years ago? Then you could have the fun of taking the mindswapped character's player into the next room and offering them a choice: either continue as the Cube or play for a while as a ringer for the DM - someone who's trying to pose as the player's previous PC but who knows nothing about the story so far, and who had their own reasons for coming down into this dungeon all those moons ago.
* No, I'm not going to model the mass to surface tension ratio or viscosity on this thing: my sense is that if it's about as dense as water and somehow manages to maintain a cube shape then it could probably be repurposed as some kind of super-material, so hand-waving is all you'll get here.
** Telecanter, when are you going to link all these posts together or provide an index page or something? This is awesome stuff and it deserves to be collated and popped on Links to Wisdom. srsly.
*** put the cube and the spheres together and you get... a big mess? Bits of caustic jelly everywhere? Deadly pinball? Something that can move the balls around so they go places gravity wouldn't just push them?
**** yes the being digested to death thing is suitably icky, but I'd guess it kills mostly by suffocation. 10' of water is considerable pressure, but not a crush attack. But if it falls on you it'll do... 2d6 per 10' of fall? And engulf you instantly.