Ooze

Oozes thrive in the dark, shunning areas of bright light and extreme temperatures. They flow through the damp underground, feeding on any creature or object that can be dissolved, slinking along the ground, dripping from walls and ceilings, spreading across the edges of underground pools, and squeezing through cracks.
The first warning an adventurer receives of an ooze's presence is often the searing pain of its acidic touch. Oozes are drawn to movement and warmth. Organic material nourishes them, and when prey is scarce they feed on grime, fungus, and offal. Veteran explorers know that an immaculately clean passageway is a likely sign that an ooze lairs nearby.
An ooze kills its prey slowly. Some varieties, such as black puddings and gelatinous cubes, engulf creatures to prevent escape. The only upside of this torturous death is that a victim's comrades can come to the rescue before it is too late.
Since not every ooze digests every type of substance, some have coins, metal gear, bones, and other debris suspended within their quivering bodies. A slain ooze can be a rich source of treasure for its killers.
Although an ooze lacks the intelligence to ally itself with other creatures, others that understand an ooze's need to feed might lure it into a location where it can be of use to them. Clever monsters keep oozes around to defend passageways or consume refuse. Likewise, an ooze can be enticed into a pit trap, where its captors feed it often enough to prevent it from coming after them. Crafty creatures place torches and flaming braziers in strategic areas to dissuade an ooze from leaving a particular tunnel or room.
According to the Demonomicon of Iggwilv and other sources, oozes are scattered fragments or offspring of the Demon Prince Jubilex . Whether this is true or not, the Faceless Lord is one of the few beings that can control oozes and imbue them with a modicum of intelligence. Most of the time, oozes have no sense of tactics or self-preservation. They are direct and predictable, attacking and eating without cunning. Under the control of Juiblex, they exhibit glimmers of sentience and malevolent intent.