Resistances protect you against several harmful effects that you may encounter in the dungeon. A resistance can be either intrinsic, meaning a natural resistance, or extrinsic, meaning a resistance gained by wearing or wielding a certain item. Many intrinsic resistances can only be gained by polymorphing into a certain creature, which is not very convenient.
One of the most common ways to gain intrinsic resistances is through the eating of corpses. Of special note are dragon corpses, as they are guaranteed to give resistances based on their color as specified below, with the exception of yellow, gray and silver. Other monsters also provide intrinsic resistances if their corpses are eaten, details of which can be found in the individual monster descriptions.
Extrinsic resistance is obtained, by definition, through items. Dragon scale mail and the lower dragon scales provide reliable methods for many resistances. Artifacts also often provide resistances, some of which are hard to obtain otherwise.
A non-exhaustive table of the resistances and methods to obtain them is as follows:
|Resistance||Dragon corpse||Dragon scales||Item||Polymorph form (see Monster resistances)|
|Acid resistance||None||Yellow||Alchemy smock||Any acidic-corpse monster (e.g. acid blob)|
|Cold resistance||White||White||Many||Many "cold" monsters|
|Disintegration resistance||Black||Black||None||(baby) black dragon|
|Fire resistance||Red||Red||Many||Many "hot" monsters|
|Magic resistance||None||Gray|| Cloak of magic resistance
Many Quest artifacts
|(baby) gray dragon|
|Poison resistance||Green||Green||Ring of poison resistance, amulet versus poison, Alchemy smock||Undead, demons, many "poisonous" monsters|
|Shock resistance||Blue||Blue||Ring of shock resistance|
|Sleep resistance||Orange||Orange||Undead, elves|
|Drain resistance||None|| Deep
The Staff of Aesculapius
|Any undead or demon|
|Stoning resistance||None||chromatic (UnNetHack only)||Acidic or stone-based creatures (e.g. gargoyles, stone golems)|
|Sliming resistance||None||None||Green slime, fiery (not merely "hot") creatures|
|Sickness resistance||None||None||Ghoul, fungi|