Gray Ooze 5e: The Ooze That Eats Your Equipment

A gray ooze is a CR 1/2 Medium ooze with AC 8 (9 in 2024), 22 hit points, a 10-foot speed and resistance to acid, cold and fire. It isn't hard to kill. It's expensive to kill: in the 2014 rules every nonmagical metal weapon that hits it takes a permanent −1 to damage (Corrode Metal), metal ammunition that hits it is destroyed, and its Pseudopod eats away at metal armor, 1 point of AC per hit. The 2024 rules widen this to every nonmagical weapon (Corrosive Form) and every nonmagical armor (Pseudopod), wood and leather included, but let the Mending spell undo the damage.

Table of Contents

• •Gray Ooze Stat Block (2014)
• •The Gray Ooze in the 2024 Rules
• •How Gray Oozes Fight
• •How Many Gray Oozes for Your Party?
• •How Players Beat Gray Oozes
• •Gray Ooze Encounter Ideas
• •Frequently Asked Questions

Gray Ooze Stat Block (2014)

The 2014 corrosion rules, step by step:

• •Weapons. A nonmagical metal weapon that hits the ooze deals its damage, then takes a permanent, cumulative −1 penalty to damage rolls. When the penalty reaches −5, the weapon is destroyed.
• •Ammunition. Nonmagical metal ammunition is destroyed after it deals damage.
• •Armor. A Pseudopod hit on a creature in nonmagical metal armor gives that armor a permanent, cumulative −1 to the AC it offers. The armor is destroyed when the penalty brings its AC down to 10.
• •Barriers. The ooze eats through 2-inch-thick nonmagical metal in 1 round. A portcullis or an iron door won't hold it.

Its False Appearance makes it look like an oily pool or wet rock while it stays still, and Amorphous lets it pass through a 1-inch gap without squeezing.

The Gray Ooze in the 2024 Rules

The 2024 change cuts both ways. A druid's wooden quarterstaff and a ranger's leather armor are no longer safe, but a cleric with Mending can fix the whole party's gear after the fight. The 2024 block prints its Initiative as "−2 (13)". An initiative score is normally 10 plus the modifier, which gives 8 for Dexterity 6, so the 13 looks like a misprint; the −2 modifier is what you roll with.

How Gray Oozes Fight

Wait to be stepped on. With a 10-foot speed, a gray ooze can't chase anyone. Its game is ambush: a puddle in a sewer, a slick patch on a cave wall (it climbs at 10 feet), a pool under a dripping ceiling. In 2014, False Appearance hides it completely. In 2024, use its Stealth +2 and dim light.

Hit the best-armored character. Against AC 16, its +3 Pseudopod hits on a 13 or better, 40% of the time. Each hit takes a point off that armor. Chain mail (AC 16) is destroyed after six hits. In a long fight with three oozes, the fighter walks out in worse armor.

Damage is modest. The 2014 Pseudopod averages 11 per hit, about 4.4 a round against AC 16. The 2024 version averages 10, about 4.0. One average hit drops most level 1 wizards.

Let the party ruin its own weapons. Every hit a fighter lands with a nonmagical sword costs the sword a point. A 2014 longsword that hits three times has −3 to damage for the rest of its life.

How Many Gray Oozes for Your Party?

A gray ooze is worth 100 XP. The 2014 Dungeon Master's Guide guidelines are in our encounter calculator.

The XP doesn't count the gear damage. A gray ooze is a resource tax as much as a fight, so give the party a way to learn what it does, like a pile of pitted, ruined swords nearby.

The ooze family. The black pudding (CR 4) is the big version: its own Corrosive Form eats weapons and armor, and it splits when hit by slashing or lightning. The ochre jelly (CR 2) splits too but doesn't corrode. The gelatinous cube (CR 2) engulfs instead. The rust monster (CR 1/2) is the gray ooze's opposite: armored, fast and hungry for metal.

How Players Beat Gray Oozes

• •Don't use metal weapons (2014). Wooden clubs, quarterstaffs, unarmed strikes and magic weapons are safe. In 2024 only magic weapons and unarmed strikes are.
• •Use spells. Magic Missile, Thunderwave, Shatter, Guiding Bolt and Eldritch Blast all deal full damage. Acid, cold and fire are halved.
• •AC 8 means everything hits. A +5 attacker hits on a 3 or better, 90% of the time. A Guiding Bolt at +5 averages 14 on a hit, so two of them kill an ooze.
• •Count your ammunition. In 2014 only nonmagical metal ammunition is destroyed, so sling stones survive. DM ruling, not rules text: arrows and bolts usually have metal heads, so decide before the fight whether they count. In 2024 every nonmagical piece of ammunition that hits is destroyed.
• •Walk away. A 10-foot speed means the party can leave and come back with a plan.
• •Mend afterward (2024). One casting of Mending removes the penalty from one weapon or one suit of armor.

Gray Ooze Encounter Ideas

The armory sump. An abandoned fort's armory is half-flooded. Two gray oozes sit in the black water among rusted spears. The weapons the party came to salvage are all useless now. One locked chest of magic weapons survived, and an ooze is sitting on it.

The drain thief. Someone in town is leaving coins in a sewer grate. A gray ooze below is eating the metal, and the town's sewer gate is gone. The guards want to know what ate an iron gate.

Trial by acid. A dwarf smith tests new blades by plunging them into a gray ooze kept in a stone tank. The ooze escaped through a drain overnight. Getting it back alive is the job.

Frequently Asked Questions

What CR is a gray ooze?

A gray ooze is CR 1/2 (100 XP) in both editions. It has 22 hit points, with AC 8 in the 2014 rules and AC 9 in the 2024 rules.

Does a gray ooze destroy weapons?

In the 2014 rules, a nonmagical metal weapon that hits it takes a permanent, cumulative −1 penalty to damage and is destroyed at −5. In the 2024 rules, any nonmagical weapon takes a −1 penalty to attack rolls after damaging it, is destroyed at −5, and can be repaired with Mending.

Can a gray ooze damage armor?

Yes. Its Pseudopod gives the target's nonmagical armor a −1 penalty to the AC it offers, metal armor only in 2014 and any nonmagical armor in 2024. The armor is destroyed when its AC drops to 10.

What is a gray ooze resistant to?

Acid, cold and fire damage. It is immune to the Blinded, Charmed, Deafened, Exhaustion, Frightened and Prone conditions, and in 2024 also Grappled and Restrained.

Stat blocks: System Reference Document 5.1 (2014) and 5.2.1 (2024), Wizards of the Coast, CC-BY-4.0. Tactics, encounter math and ideas are Loreify's own.