n large mindless ooze 

Perception +5; motion sense 60 feet, no vision

Skills Athletics +11 (+13 to Shove)

Str +4 Dex -5 Con +5 Int -5 Wis +0 Cha -5

Motion Sense A sewer ooze can sense nearby motion through vibration and air movement.

Transparent A gelatinous cube is so clear that it's difficult to spot. A successful DC 23 Perception check is required to notice a stationary cube, and a creature must be Searching to attempt this check. A creature that walks into the cube is automatically Engulfed (this usually causes the GM to call for initiative).

AC  10; Fort +12, Ref +0, Will +5

HP 90; Immunities acid, mental, precision, critical hits, unconscious, visual

Speed 15 feet

Melee [>] cube face +11, Damage 1d6 acid plus paralysis

Engulf [>>] DC 19, 2d6 acid, Escape DC 19, Rupture 7. A creature Engulfed by the gelatinous cube must also attempt a saving throw against paralysis.

Paralysis (incapacitation) A creature Engulfed by the cube or hit by its attack is paralyzed unless it succeeds at a DC 20 Fortitude save. A victim can attempt a new save to recover at the end of each of its turns.

Weak Acid A gelatinous cube's acid damages only organic material—not metal, stone, or other inorganic substances.

Bestiary, page 254. Expanded in LOIL.