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 damage can come from several sources, all of which can cause what is known as an "acid splash" (indicated by the message "The acid burns!"). The additional damage from an acid splash is 4d3 from melee-based sources and 4d5 from ranged sources; monsters only receive 2d4 extra damage from melee attacks and are not subject to ranged acid splashes.
Acidic Melee Attacks
The following monsters have acidic melee attacks, which cause an acid splash and may apply corrosion:
J 
Jelly
Spit Acid
The following monsters can Spit Acid as a ranged attack, dealing 3d7 acid damage that bypasses AC and may incur both an acid splash and corrosion:
Acid Splash
Yellow draconians (which occasionally includes Tiamat) may use the Acid Splash ability. This is similar to Acid Spit but may splash onto additional creatures adjacent to the target.
d 
Tiamat
Acidic Flesh
Some monsters have acidic flesh and will cause acid splashes when attacked with a melee weapon:
J Jelly
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 wand of clouds.
Slime Walls
Standing next to the walls of the Slime Pits will subject players and non-jelly or -eyeball monsters to one acid splash per wall tile. Unlike most other types of acid damage, this will never inflict the corrosion status.
Worshipers of Jiyva are unaffected by slime walls.
Corrosion Resistance
Corrosion resistance reduces damage taken from acid and reduces the chance of being further corroded.
The sources of Corrosion resistance are:
- being a yellow draconian
- Ring of resist corrosion
- Acid dragon scales
- 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 which gives a stackable -4 to slaying and AC for as long as it lasts. All corrosion will be repaired after enough time has passed. It can also be removed with a potion of cancellation or by aiming Yara's Violent Unravelling or your own purple draconian breath at yourself.
In addition to taking acid damage, players may also suffer corrosion from these sources:
- The Entropic Weave spell of a
Entropy weavers - Taking damage when wearing an artefact with the *Corrode property.
Monsters that have been corroded simply get a temporary -8 to their AC. This does not stack -- additional corrosion merely increases the duration.
History
- 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.
- 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.
