Stunjelly

A stunjelly was a rare ooze that appeared much like a stone wall.

Description
Stunjellies were the experimental products of a mage of unknown name. They were relatives of gelatinous cubes, but were not transparent. Instead, they were slightly translucent, and had a cuboid shape, much like a wall. Thus, it wasn't as easy to see the treasure floating in their interior; in normal light, stunjellies looked identical to normal stone walls. These jellies were approximately in length, and were about  thick. Unlike their cousins, the gelatinous cubes, and many other oozes, stunjellies had animal-like intelligence, instead of non-intelligence.

These oozes reproduced via fission, and when they did, they emitted loud and violent sounds.

Combat
These jellies did not need to actively travel to hunt prey. Instead, when their prey walked past them (most often at night ), their soporific pseudopods would reach out and paralyze them. The jellies' foes could be stunned for up to two minutes, making it almost impossible to escape before being fully digested.

Like their cubic, transparent cousins, they were immune to all sources of electrical damage. Stunjellies also could not be paralyzed, charmed, or made to change form, such as via a polymorph spell.

Ecology
Unlike other oozes, stunjellies were actually mostly tolerated by others, particularly those that watched over dungeons. As they could not change form to move through doors or other gaps, they could be contained in a specific place. Here, they could mop up the remains of litter and serve as traps for those who were not welcome.

History
As of the 14 century DR, stunjellies could be found in the sewers of Waterdeep.