Monster Manual p.243
Stealth +2
Blindsight 60ft. (blind beyond this radius), Passive Perception 8
Amorphous. The pudding can move through a space as narrow as 1 inch wide without squeezing.
Corrode Metal. Any nonmagical weapon made of metal that hits the ooze corrodes. After dealing damage, the weapon takes a permanent and cumulative -1 penalty to damage rolls. If its penalty drops to -5, the weapon is destroyed. Nonmagical ammunition made fo metal that hits the ooze is destroyed after dealing damage.
The ooze can eat through 2-inch-thick, nonmagical metal in 1 round.
False Appearance. While the ooze remains motionless, it is indistinguishable from an oily pool or wet rock.
Pseudopod. Melee Weapon Attack: +3 to hit, reach 5ft., one target. Hit: 4 (1d6+1) 1d6+1 bludgeoning damage plus 7 (2d6) 2d6 acid damage, and if the target is wearing nonmagical metal armor, its armor is partly corroded and takes a permanent and cumulative -1 penalty to the AC it offers. The armor is destroyed if the penalty reduces its AC to 10.
Psychic Crush (Recharge 5–6 1d6 ). The ooze targets one creature that it can sense within 60 feet of it. The target must make a DC 10 Intelligence saving throw, taking 10 (3d6) 3d6 psychic damage on a failed save, or half as much damage on a successful one.
Slow Death. 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.
Unwitting Servants. 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.
Spawn of Juiblex. According to the Demonomicon of Iggwilv and other sources, oozes are scattered fragments or offspring of the demon lord Juiblex. 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.
Ooze Nature. An ooze doesn’t require sleep.
A gray ooze is stone turned to liquid by chaos. When it moves, it slithers like a liquid snake, rising to strike.
False Appearance. While the ooze remains motionless, it is indistinguishable from an oily pool or wet rock.
VARIANT: PSYCHIC GRAY OOZE
A gray ooze that lives a long time can evolve to become more intelligent and develop limited psionic ability. Such occurrences are more common in gray oozes that live near psionic creatures such as mind flayers, suggesting that the ooze can sense and mimic psionic ability.
A psionic gray ooze has an Intelligence score of 6 (−2), as well as the following additional action.
Psychic Crush (Recharge 5–6 1d6 ). The ooze targets one creature that it can sense within 60 feet of it. The target must make a DC 10 Intelligence saving throw, taking 10 (3d6) 3d6 psychic damage on a failed save, or half as much damage on a successful one.
They are mostly subterranean, dwelling in caves and Dungeons and feeding on refuse, carrion, or Creatures unlucky enough to get in their way. Black puddings and gelatinous cubes are among the most recognizable oozes.