Acid
Acid is a damage type most commonly dealt by jellies and acidic dragonkind, which can be resisted with corrosion resistance. Most types of acid damage can apply a temporary corrosion status, which lowers your AC and slaying.
Contents
Sources of Acid
Acidic Melee Attacks
The following monsters have acidic melee attacks, which may apply corrosion:
- J
Jelly - J
Acid blob - J
Dissolution - J
The royal jelly - b
Caustic shrike - u
Brown ugly things and very ugly things
Acidic melee attacks may cause an "acid splash" (the message "the acid burns!"). Players receive 4d3 extra damage, and monsters only receive 2d4 extra damage.
Acidic Flesh
Some monsters have acidic flesh and will cause acid splashes when attacked with a melee weapon, like the extra "splash" from the melee attack (4d3 vs players):
- J Jelly
- J Acid blob
- J Dissolution
- J The royal jelly
Spit Acid
The following monsters can Spit Acid as a ranged attack, dealing 3d14 acid damage that bypasses AC and may incur corrosion:
- J Acid blob
- D
Acid dragon - P
Oklob plant - P
Oklob sapling - d
Yellow draconian - d
Tiamat
Player yellow draconians may use the Acid Splash ability, which is like Spit Acid but can hit surrounding enemies. Neither Spit Acid nor Acid Splash ability have the "acid splash" of melee attacks.
Corrosive Bolt
The spell Corrosive Bolt deals significant acid damage and may inflict corrosion. Several monsters may cast it, as well as any creature that has picked up a wand of acid.
The following enemies cast Corrosive Bolt:
- L
Ancient lich (3d34 damage) - e
Deep elf sorcerer (3d21 damage) - T
Moon troll (3d25 damage) - D
Serpent of Hell (Tartarus) (3d24 damage) - Q
Tengu reaver (3d24 damage)
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The following enemies may be able to cast Corrosive Bolt, depending on their spell set:
- &
Pandemonium lord (5.2% chance)
Acidic Fog
Acidic fog is a type of cloud that deals acid damage to and corrodes anything unfortunate enough to be standing in it. It can only be produced by a high-powered condenser vane.
Corrosion Resistance
Corrosion resistance reduces damage taken from acid and reduces the effect of corrosion. Also, it gives immunity to clouds of acidic fog.
The sources of Corrosion resistance are:
- being a yellow draconian
- cloak of preservation
- ring of resist corrosion
- acid dragon scales
- artefacts with rCorr
- potion of resistance
- Tiamat's dragonskin cloak (50% chance per attack)
- Having the yellow scales mutation at level 3
- Having at least ** piety while following Jiyva
Damage Reduction
Players with corrosion resistance take 50% damage from acid. All monsters with any degree of acid resistance are completely immune to acid damage.
Corrosion
Corrosion is a temporary status effect.
On players, it gives a stackable -4 to damage roll and AC for its duration. Players with corrosion resistance will only take a -2 penalty per application. All corrosion will be repaired after enough time has passed. It can be immediately removed with a potion of cancellation or other dispelling effects (Yara's Violent Unravelling, Quicksilver Bolt, or your own purple draconian breath).
In addition to acid damage, players may also suffer corrosion from these sources:
- Being hit by enemies with corrosive attacks (like the 4
Rust devil). - The Entropic Weave spell of B
Entropy weavers or 6 
Demonspawn corrupters - Taking damage while wearing an artefact with the *Corrode property (3% chance per *Corrode).
- Being adjacent to slime covered rock. (Corrosion will cease as soon as you move away from the wall.)
Monsters that have been corroded get a temporary -8 to their AC. This does not stack -- additional corrosion merely increases the duration.
History
- Prior to 0.32, corrosion resistance did not reduce the effect of corrosion. Instead, it had a 50% chance to prevent each application of corrosion.
- Prior to 0.30, slime-covered walls in the Slime Pits would inflict acid damage.
- Prior to 0.28, Spit Acid, Acid Splash, and Corrosive Bolt caused additional "acid splashes" (extra 4d5 v. the player, 2d4 v. monsters). Their base damage was lower to compensate.
- Prior to 0.15, corrosion instead caused permanent damage to weapons and armour, reducing their enchantment values, possibly into the negatives. Also, potions of resistance did not grant rAcid or rCorr.
- There were previously three tiers of acid resistance, each one further reducing acid damage; now there is only one level which is merged with corrosion resistance.
- In previous versions, acid splashes did more damage if you were wearing less armour (2 dice plus an additional die for each empty armour slot); cloaks provided a 50% chance per empty slot of negating this extra damage, and the damage was reduced by having the fur mutation.
