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Version 0.14: This article may not be up to date for the latest stable release of Crawl.

Acid is a damage type that can be reduced by filling as many of your armour slots as possible. This protection comes at a price, as every piece of armour worn has a chance of being temporarily corroded.

Sources of Acid

Acidic damage can come from several sources.

Acidic Flesh

Some monsters have acidic flesh:

Hitting such monsters with a melee weapon (or any wielded piece of armour) has a 30% chance of corroding that weapon. If you are wielding nothing but wearing gloves, your gloves may corrode. If you are completely bare-handed, you will take 1d5 acid damage. Attacks other than punches (e.g. auxiliary kicks, tail slaps, etc.) will not incur damage or corrosion.

Acid Spit

The following monsters can spit acid:

The above damage bypasses AC. In addition to the above damage, acid spit causes 5 levels of "acid splash" damage (described below) which will harm you and can corrode your armour.

Acidic Melee Attacks

The following monsters have acidic melee attacks:

When struck by these monsters in melee, you will receive 3 levels of acid splash damage in addition to any regular (physical) damage the attack causes.

Slime Walls

Standing next to the walls of the Slime Pits will cause one level of acid splash damage for every level of depth, reaching 6 levels of splash damage on Slime:6. This damage is applied by every wall you are adjacent to: if you are surrounded by walls on Slime:1, you will receive eight separate level 1 splashes. Monsters without acid resistance will receive a flat 2d(level) damage from each wall.

Worshipers of Jiyva are unaffected by slime walls.

Thankfully, the acid splash from slime walls does not corrode items. But given how many monsters in the slime pits have corrosive attacks, this is of limited consolation.

Acid Splash

An acid splash will strike every armour slot - shield, helmet, body armour, gloves, boots, and cloak - with a chance of corroding each equal to the splash's level * 5%. If you are wearing a cloak, it has a 50% chance of negating a successful corrosion against the helmet, body armour, gloves, and boots slots (each rolled separately). This protection will not harm the cloak, which can only sustain damage when the cloak slot is corroded.

If you are not wearing armour in a given slot (excepting the shield slot), you will take 1d(splash level) damage (a cloak's 50% negation chance can also protect you from this). The fur mutation (trolls and felids) will reduce this damage by 20% per level of mutation.

2d(splash level) damage is then added to the above, meaning a splash can cause anywhere from 2dX to 7dX damage. Finally, the total damage is reduced by your acid resistance, as shown below.

Acid Resistance

Acid resistance protects you from any damage that gets past your armour. It is distinct from corrosion resistance, which protects your weapon and armour.

The sources of acid resistance are:

The maximum resistance possible is rAcid+++.

Damage Reduction

Resistance Level Damage Taken (Player) Damage Taken (Monster)
1 50% 0%
2 34% 0%
3 27% 0%

Any fractional amount remaining is rounded down (if you get hit with 3 points of acid damage and you have rAcid+, you will only take 1 point of damage; if you have rAcid+++, you will take no damage). Acid resistance is effective against acid spit and splashes but does not reduce the damage received when punching an acidic monster.

All monsters with any degree of acid resistance are completely immune to acid damage.


Corrosion is a temporary status effect which gives a stackable -4 to slaying and AC for as long as it lasts. Corrosion will be repaired after enough turns have passed.


Prior to 0.15, corrosion instead caused permanent damage to weapons and armor, reducing their enchantment values, possibly into the negatives. Also, potions of resistance did not grant rAcid or rCorr.