Acidic Gelatinous Cube

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Large Ooze, Neutral

Armor Class 12 (natural armor)

Hit Points 95 (10d10+40)

Speed 15 ft.

STR 18 (+4)

DEX 3 (-4)

CON 14 (+2)

INT 2 (-4)

WIS 10 (+0)

CHA 1 (-5)

Skills Perception +3

Damage Immunities poison

Condition Immunities blinded, charmed, frightened, poisoned

Senses darkvision 60 ft., passive Perception 13

Languages —

Challenge 6 (2,300 XP) Proficiency Bonus +3

Legendary Resistance (3/Day). If the creature fails a saving throw, it can choose to succeed instead.

Acidic Slime. Whenever the cube is dealt acid damage, it regains a number of hit points equal to the acid damage dealt (to a maximum equal to its normal HP).

Engulfing Sludge. The cube can attempt to engulf a Medium or smaller creature that is in its space. A creature so engulfed is restrained and takes 14 (4d6) acid damage at the start of each of the cube's turns. An engulfed creature can escape with a successful DC 15 Strength check. The cube can have only one creature engulfed at a time.

Actions

Multiattack. The cube makes two Slam attacks.

Slam. Melee weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 16 (3d6+6) bludgeoning damage. A brutal shove or bite of acidic slime rips into a target.

Engulf (Recharge 5-6). Hit: 14 acid damage. If the cube moves into a creature's space and that creature is Medium or smaller, it can attempt to engulf it. The engulfed creature is restrained and takes 14 (4d6) acid damage at the start of each of the cube's turns. The engulfed creature can escape with a successful DC 15 Strength check on its turn.

Environment Underdark

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Lore & Description

Appearance

A gleaming, translucent emerald-green cube of viscous ooze writhes with bubbling pockets of acid. Its edges glisten with corrosive liquid, and the interior occasionally glows with a sickly light as swallowed minerals dissolve. The cube's surface shimmers when acid is spilled on it, and it leaves a faint corrosive trail wherever it moves.

Behavior & Origins

Acidic Gelatinous Cubes dwell in damp, rarely-traveled tunnels in the underdark and places where acid seepage has dissolved the rock. They are patient, patient killers: they slowly consume intruders by engulfing them, then digest them entirely. Those who survive encounters with an acidic gelatinous cube tell tales of their sharp, caustic taste and their desire to spread its corrosive essence to new locations by dissolving rock and rock-eaten debris into more of its own substance.

Monster Image

Generation Info

Original prompt:
"acidic gelatinous cube"

Created: Feb 5, 2026
Modified: May 29, 2026