Gray Ooze – The Silent Corrosion
At a Glance
| Creature | Gray Ooze — a mindless, corrosive predator |
|---|---|
| Size | Medium, spreading thin against damp stone |
| Temperament | Unaligned; not malicious, only hungry |
| Habitats | Cold marshes, drains, cellars and forgotten tunnels |
| Warning signs | Metal eaten away, oddly wet flagstones, a silent shimmer |
| Greatest danger | Acid capable of destroying gear and flesh |
| Movement | Slow, nearly shapeless, hard to distinguish from puddles |
The water is climbing the wall. Beneath the stairs, a silver buckle has melted into the flagstones. What looked like a wet stain extends a blind pseudopod towards a companion’s sword and the blade begins to hiss.
A Hungry Stain in the Stone
A gray ooze can spread itself across a block of masonry until a room seems merely damp. It has no voice, eyes or plans. It detects prey within its primitive senses, then lashes out with acidic tendrils that eat the things a traveller carries as readily as living flesh. The ruin is not haunted by a patient monster; its danger is a predator that looks like part of the floor.
Though it cannot bargain or obey a command, it may be confined behind a dry stone ledge or steered by the movement of food. Miners and sewer workers learn to examine metal fittings before trusting an apparently empty passage. A sword blade ruined by corrosion can tell them more than a thousand tracks. Unlike the Gelatinous Cube, this predator does not swallow an entire corridor: its acid quietly destroys the gear carried through it. Its greater cousin, the Black Pudding, can turn careless slashing attacks into a second hungry creature.
Running the Encounter
Give the party a clue before asking for the applicable edition’s detection roll: a half-eaten nail, a spur disappearing into stone or a trail of corrosion leading beneath a locked door. Once the ooze strikes, players can retreat to dry ground, use a hooked pole or place a grate between it and their armour. The 2024 and 2014 corrosion mechanics differ from Pathfinder and 3.5e; the chosen stat block decides exactly what equipment survives.
Game Statistics
Gray Ooze
Medium Ooze, Unaligned
Armor Class 9
Initiative −2 (8)
Hit Points 22 (3d8 + 9)
Speed 10 ft., Climb 10 ft.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 12 (+1) | 6 (−2) | 16 (+3) | 1 (−5) | 6 (−2) | 2 (−4) |
Saving Throws Str +1, Dex −2, Con +3, Int −5, Wis −2, Cha −4
Skills Stealth +2
Resistances Acid, Cold, Fire
Immunities Blinded, Charmed, Deafened, Exhaustion, Frightened, Grappled, Prone, Restrained
Senses Blindsight 60 ft.; Passive Perception 8
Languages None
Challenge 1/2 (100 XP)
Proficiency Bonus +2
Traits
Amorphous. The ooze can pass through a gap only one inch wide without spending extra movement.
Corrosive Form. Nonmagical ammunition that hits and damages it is destroyed. A nonmagical weapon that hits and touches the ooze takes a cumulative −1 penalty to its attack rolls; it is destroyed when the penalty reaches −5. The Mending spell removes this penalty. The ooze can eat through two inches of nonmagical metal or wood in one round.
Actions
Pseudopod. Melee Attack Roll: +3 to hit, reach 5 ft., one target. Hit: 10 (2d8 + 1) Acid damage. Nonmagical armour worn by the target takes a cumulative −1 penalty to its AC; the armour is destroyed if the AC it offers is reduced to 10. The Mending spell removes this penalty.
Gray Ooze
Medium ooze, unaligned
Armor Class 8
Hit Points 22 (3d8 + 9)
Speed 10 ft., climb 10 ft.
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 12 (+1) | 6 (−2) | 16 (+3) | 1 (−5) | 6 (−2) | 2 (−4) |
Skills Stealth +2
Damage Resistances acid, cold, fire
Condition Immunities blinded, charmed, deafened, exhaustion, frightened, prone
Senses blindsight 60 ft. (blind beyond this radius), passive Perception 8
Languages —
Challenge 1/2 (100 XP)
Traits
Amorphous. The ooze can move through a space as narrow as one inch without squeezing.
Corrode Metal. Any nonmagical metal weapon that strikes the ooze corrodes. The weapon takes a cumulative −1 penalty to damage rolls after dealing damage, and is destroyed at −5. Nonmagical metal ammunition that hits is destroyed after damage. The ooze can dissolve two inches of nonmagical metal in one round.
False Appearance. The ooze is indistinguishable from a wet rock or pool of oil while motionless.
Actions
Pseudopod. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) bludgeoning damage plus 7 (2d6) acid damage. If the target wears nonmagical metal armour, that armour takes a cumulative −1 penalty to the AC it offers and is destroyed if the AC is reduced to 10.
Gray Ooze — CR 4
XP 1,200; N Medium ooze; Init −5; Senses blindsight 60 ft.; Perception −5
DEFENSE
AC 5, touch 5, flat-footed 5 (−5 Dex)
hp 50 (4d8 + 32)
Fort +9, Ref −4, Will −4
Defensive Abilities ooze traits; Immune cold, fire
OFFENSE
Speed 10 ft.
Melee slam +6 (1d6 + 4 plus 1d6 acid and grab)
Space 5 ft.; Reach 5 ft.
Special Attacks acid, constrict (1d6 + 1 plus 1d6 acid)
STATISTICS
| STR | DEX | CON | INT | WIS | CHA |
|---|---|---|---|---|---|
| 16 (+3) | 1 (−5) | 26 (+8) | — | 1 (−5) | 1 (−5) |
Str 16, Dex 1, Con 26, Int —, Wis 1, Cha 1
Base Atk +3; CMB +6 (+10 grapple); CMD 11 (can’t be tripped)
Skills —; Feats —; Languages —; SQ transparent
ECOLOGY
Environment cold marshes and underground
Organization solitary
Treasure none
SPECIAL ABILITIES
Acid (Ex). Its acid dissolves metal and organic matter, but not stone. Slam and constrict each deal an additional 1d6 acid damage. Armour and clothing worn by a grappled creature suffer acid damage unless the wearer succeeds on a DC 20 Reflex save. A wood or metal weapon that strikes the ooze takes 1d6 acid damage unless its wielder passes a DC 20 Reflex save. Contact for a full round deals 12 acid damage to wooden or metal objects; the saving throw DC is Constitution-based.
Transparent (Ex). Noticing the ooze requires a DC 15 Perception check. Someone who walks into an unnoticed ooze is automatically struck by its slam and exposed to a grab attempt.
Gray Ooze — CR 4
Medium Ooze; always Neutral
Hit Dice 3d10 + 15 (31 hp)
Initiative −5
Speed 10 ft. (2 squares)
Armor Class 5 (−5 Dex), touch 5, flat-footed 5
Base Attack/Grapple +2/+3
Attack slam +3 melee (1d6 + 1 plus 1d6 acid)
Full Attack slam +3 melee (1d6 + 1 plus 1d6 acid)
Space/Reach 5 ft./5 ft.
Special Attacks acid, constrict (1d6 + 1 plus 1d6 acid), improved grab
Special Qualities blindsight 60 ft., immunity to cold and fire, ooze traits, transparent
Saves Fort +6, Ref −4, Will −4
Abilities Str 12, Dex 1, Con 21, Int —, Wis 1, Cha 1
Skills —; Feats — (mindless)
Senses blindsight 60 ft.; Listen −5, Spot −5
Languages —
Environment cold marshes
Organization solitary
Challenge Rating 4
Treasure none
Alignment always neutral
Advancement 4–6 HD (Medium), 7–9 HD (Large)
Level Adjustment —
Special Abilities
Acid (Ex). Its digestive acid corrodes organic materials and metal, leaving stone intact. Clothing or armour struck must pass a DC 16 Reflex save or be destroyed; metal or wood weapons that touch it must also pass a DC 16 Reflex save. Sustained contact deals 16 acid damage per full round to metal or wood.
Constrict (Ex). A successful grapple check inflicts its slam and acid damage automatically, and clothing or armour takes a −4 penalty on its save against the acid.
Improved Grab (Ex). A slam hit allows a free grapple attempt without provoking an attack of opportunity. A successful grapple permits constriction.
Transparent (Ex). Spotting the still ooze takes a DC 15 Spot check. Walking into it unnoticed triggers a slam and acid damage.
Resolve attacks, corrosion and grapple effects using the selected edition. These four versions are not interchangeable.
Variant Gray Oozes
Crystal Ooze
Pathfinder 1e variant: CR 4. This aquatic creature swims at 30 feet but loses the normal ooze’s constrict attack. Its touch delivers a paralytic toxin: a failed Constitution-based Fortitude saving throw leaves a victim paralyzed for 3d6 rounds.
Id Ooze
Pathfinder 1e variant: CR 6. A rare gray ooze acquires a flicker of intellect (Intelligence 2). It gains skill ranks and feats, including Stealth, Improved Initiative and Toughness, and can communicate simple emotion with other id oozes within 100 feet by telepathy. Its oldest reported form can use lesser confusion at will, with caster level equal to its Hit Dice. These features belong to the variant, not to ordinary gray oozes.
Encounters in the Deep
The Door Without a Lock
An old merchant’s iron vault still stands intact, yet the wooden floor beside it has dissolved and every hinge is thin as paper. Inside lies a prisoner accused of selling enchanted weapons. The vault can be opened, but the slow wet stain beneath the threshold has already touched the guards’ armour. Rescue the captive, recover the ledger or let the ooze finish the work it began.
The Wet Stair
Refugees shelter in a cellar beneath a flooded keep, and the only staircase is always damp. A child’s iron toy has vanished and the baker’s knife has turned to flakes. The ooze is inching toward the sleeping room. The party can drive it into a dry chamber, raise the stone floodgate or lure it through the older drain before it reaches the families.
Rules Sources
D&D 2024 Gray Ooze · D&D 2014 Gray Ooze · Pathfinder 1e Gray Ooze · D&D 3.5e Gray Ooze. The versions retain their edition’s original distinctions. Open rules are credited to Wizards of the Coast or Paizo under the applicable SRD or open game licences. The Crystal Ooze and Id Ooze are legacy Pathfinder-era variants and are not standard versions in every edition.
Other oozes: Green Slime · Garden Ooze, Ochre Jelly, Giant Amoeba, Plasma Ooze and Fiendish Elder Black Pudding.
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