The gelatinous mass is like a gelatinous cube, but is has a mind and is intelligent. Some have hinted that the origin of the gelatinous mass is with mind flayers. A bit of brain material, having escaped the vat of the elder brain, the result of a mind flayer being consumed by a gelatinous cube, or the result of a genetic experiment.



The gelatinous mass has all of the features of gelatinous cube. It also has calculating intelligence with a utterly alien perspective. The gelatinous mass, differs from the cube, that it does not dissolve neural material, instead incorporating neural material of its victims into it’s system.

D&D 5e stat block (OSR version)

Gelatinous Mass

Large intelligent ooze, neutral

Armor class: 6

Hit points: 84 (8d10+40)

Speed: 15 ft.

Str: 14 (+2) Dex: 3 (-4) Con: 20 (+5) Int: 14 (+2) Wis: 12 (+1) Cha: 10 (0)

Condition immunities: deafened, exhaustion, prone, poisoned

Senses: dark vision 60 ft. Detect thoughts 300 ft. the gelatinous mass can detect the mental activity of intelligent creatures up to 300 ft. away. It does not read minds, or know the nature of these thoughts only that an intelligence exists.

ACTIONS

Pseudopod. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 10 (3d6) acid damage.

Engulf. The cube moves up to its speed. While doing so, it can enter Large or smaller creatures’ spaces. Whenever the cube enters a creatures space, the creature must make a DC 12 Dexterity saving throw. On a successful save, the creature can choose to be pushed 5 feet back or to the side of the cube. A creature that chooses not to be pushed suffers the consequences of a failed saving throw. On a failed save, the cube enters the creature’s space, and the creature takes 10 (3d6) acid damage and is engulfed. The engulfed creature can’t breathe, is restrained, and takes 21 (6d6) acid damage at the start of each of the cube’s turns. When the cube moves, the engulfed creature moves with it. An engulfed creature can try to escape by taking an action to make a DC 12 Strength check. On a success, the creature escapes and enters a space of its choice within 5 feet of the cube.

Mental confusion: intelligent creatures within 100′ begin to sense the thoughts of the gelatinous mass. These are are an incoherent collage of random images and sensations from do of the creatures absorbed by the mass. Intelligent creatures within 100′ must make a DC 8 wisdom saving throw. On failure, the creature can’t take reactions until the start of the next turn and rolls a d8 to determine what it does during its turn.

1-4 the creature does nothing .

the creature does nothing . 5-6 the creature takes no action or bonus action and uses all of its movement to move in a random direction.

the creature takes no action or bonus action and uses all of its movement to move in a random direction. 7-8 makes a melee attack against a randomly chosen target within range, or does nothing at all.

I imagine this creature lurking in a dark maze of corridors. It’s mental confusion causing disarray in the party as they get near. The confusion ability seemed too good with a 100′ range. In game terms 100′ is huge, 20 squares! In real life it’s not that far, maybe the size of a large Starbucks. What do you think?