Acid resistance

Acid resistance is a property that appears in NetHack and protects against acid damage. It does not protect your equipment against acidic erosion – this is done by corrodeproofing it.

Sources

Acid resistance can be obtained extrinsically by wearing yellow dragon scales, yellow dragon scale mail, or an alchemy smock. As an intrinsic, it can only be obtained by polymorphing into a monster with intrinsic acid resistance (e.g. any acidic monster).

Strategy

Despite the resistance's rarity, it is not that worthwhile, as sources of acid damage are uncommon - even in scenarios where the acid does significant damage, it can often be easily avoided by other methods. Yellow dragon scales may still be worthwhile for pets and polyforms with multiple hit dice, particularly mind flayers.

Variants

SLASH'EM

In SLASH'EM, the alchemy smock has been replaced by the lab coat, which also provides this extrinsic. Acid resistance is still not usually considered necessary for ascension, but some new monsters in SLASH'EM, most notoriously the giant shoggoth, deal massive amounts of acid damage and therefore a player who has magic resistance, reflection, drain resistance, and magic cancellation through other means may opt for yellow dragon scale mail just to be on the safe side.

FIQHack

In FIQHack, extrinsic acid resistance protects your items from corrosion.

EvilHack

In EvilHack, acid resistance is far more vital in comparison to vanilla, due to the presence of monsters such as acid spheres and the highly-damaging acid blast monster spell, which can additionally corrode items in your inventory. Dragonbane is also changed to a pair of dragonhide gauntlets that provide acid resistance in addition to the standard reflection and warning of dragons, making it a highly sought-after wish for most players.