I recently ran a game in which my PCs were trapped in a hallway with a gelatinous cube on either end. They killed one of the cubes, but I didn't know whether or not the corpse of the cube is still blocking the space. I ended up ruling that the PCs had to cut their way through in order to bypass the corpse.

According to the Monster Manual (p. 242),

The [gelatinous] cube takes up its entire space.

As I understand, this is a classic and unique feature of the gelatinous cube, allowing it to completely blockade a 10x10 hallway. However, it does not say if it continues to take up its entire space after it's dead. Are there any resources, including in previous editions, that specify this?


2 Answers 2


This old issue of Dragon 124 might help a bit with your question. It was a resource back in the day, though it's not 5e. You asked for any resources including those using old editions--and that article is a treasure trove of useful info you can use.

One particular bit on page 57 of the issue:

As to their digestive fluids these are produced and held in movable, elastic cavities or bubbles within an athcoids body. When prey is engulfed by a cube, one or more of these mobile bubbles are shifted into contact with the prey. Such fluid has no effect on metal of any sort, and, as we have all heard, metal objects are held for a time within the creature, then expelled through its skin; but the fluid has devastating effects on flesh and cellulose.

I would posit, based on this that the cavities or bubbles are maintained within the creature, and that upon death, they deflate and the creature loses cohesion.

It's DM call on if the acid of the cube still has an effect after it's "killed." What I have done, as it loses hit points is allow it to puddle in the hall around the PCs. For about a round it remains acidic--but that's a DM call there. As they take away the hit points from the creature, it does naturally move toward warmth vibration and sound, so even if it is a bit shorter, it will try to block their way.

Once it's dead, all that mass has to go somewhere, and I work it like a gel-filled balloon that's been popped. But--you can work it the way you did, ruling that it maintains cohesion for up to an hour after death or more, or less, that's your call as the DM.

I have also had some fun with PCs once they have defeated the creature by having the gel start to coalesce again--remaining bits into baby cubes. The PCs were so freaked out by it shifting to come together again that they simply ran away, despite the fact that the baby cubes would have moved away from them as they are now too big to eat. That isn't at all canon--I just like throwing something their way they haven't seen.

Not all cubes are going to be the same--I use the MM as a jumping off point and assume that some creatures in an isolated dungeon might have developed slightly differently. It also keeps my players from metagaming too much--if they are of a particular level, they expect specific creatures in their range, which is annoying, because they will try to use out of game knowledge to fight said creatures.

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    \$\begingroup\$ I'm amazed you managed to make your PCs run away. Mine would have melted their boots (and/or feet) stomping the increasingly small cubes even if just for the slight chance that they award a bit of XP \$\endgroup\$
    – xDaizu
    Commented Jun 19, 2017 at 13:26
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    \$\begingroup\$ @xDaizu By this time they were low on HP, resources and spells. The baby cubes hadn't fully formed, the goo was just starting to come together. I think normally, yes they would have waited so they could get an XP award, but those things on top of an unsettling description made them fear that the entire cube was reforming. When I run they know that the monsters could follow different rules. \$\endgroup\$ Commented Jun 19, 2017 at 14:56

Even if this was officially stated in the MM, the real answer would depend on your player group. If you have a high action group that enjoys combat, having the dead ooze block the path could add a low action point to your adventure. However if the group tends to be problem solvers, blocking the path this way could actually intrigue them with a 'puzzle reward' for the combat. If they struggle with the puzzle (or this group is not well known to you (a publicly run game)) you could always have the ooze 'slide downhill' into a pit trap.

Since people seem to like this answer; here is quick way to gage a player group if you don't know them well; When the fight ends, ask the group what they do next. They will:

  • Charge ahead, then allow assumption the monster does not block the hall
  • Ask you about the monster's remains or try to search them, this is your discretion to allow it to slide away and create and acid pit
  • Start describing or discussing how to remove its remains, let them problem solve it then
  • Opt to camp or return up the path, since they ignore it, let it be assumed as it vanished unless they make further note of it (trying to harvest goo when camping)
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    \$\begingroup\$ I think letting the players' play-styles influence their adventures is the best approach to DMing in general. \$\endgroup\$ Commented Jun 19, 2017 at 18:38

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