The yellow dragon, D, is a monster that appears in NetHack. It has a younger form in the baby yellow dragon, D. The yellow dragon has acid resistance both intrinsically and from its scales, and as an acidic monster it is also immune to stoning; its breath weapon fires rays of acid. Its corpse is also acidic, but does not convey any resistances.
Players will not see baby yellow dragons through normal random monster creation outside of the Oracle and Sokoban levels, and they can also be hatched from dragon eggs; adult yellow dragons start appearing around the midway depths of the dungeon. Yellow dragons can be generated in throne rooms as early as dungeon level 15, and may appear when a throne at this depth or lower is looted. Yellow dragons can be generated if a lawful spellcaster casts the summon nasties monster spell.
In addition, the fourth variant of Medusa's Island has a yellow dragon generated asleep behind Medusa's dwelling; she nests on 1-3 baby yellow dragon eggs, and there may be up to two live babies sleeping next to her.
The yellow dragon's acid blasts can ruin metal armor and weapons unless they are corrodeproofed, making it dangerous to be caught down line-of-sight from one (though not to the same extent as other dragons like the black dragon). Its breath weapon can be deflected with reflection, thankfully - for players lacking reflection, however, it has the fewest means of direct resistance available. Even the black dragon's disintegration has a resistance that can be gained intrinsically, albeit only by eating its meat or that of the poisonous Chromatic Dragon. Conversely, acid resistance cannot be gained intrinsically except by taking the form of an acidic monster, and is only granted extrinsically via yellow dragon scales, yellow dragon scale mail, or an alchemy smock.
While not desired to nearly the same extent as those of a gray or silver dragon, yellow dragons are sometimes worth seeking out for their scales to give a humanoid pet resistance against dangerous acid passives - especially if that pet has multiple attacks, e.g., a tamed (master) mind flayer. Yellow dragons themselves are solid choices for stoning-resistant pets, being among the strongest acidic monsters in the game.
NetHack 2.3e introduces the yellow dragon along with all of the other modern dragon types and their breath weapons, except for silver.
NetHack 3.0.0 introduces baby yellow dragons alongside the other baby dragons. This version also distinguishes all color dragons, their younger stages and their corpses, and introduces dragon scale mail.
NetHack 3.1.0 introduces yellow dragon scales along with the other colors, as well as the current method of obtaining dragon scale mail.
The version of Medusa's island with the guaranteed yellow dragon and her offspring was introduced in NetHack 3.6.0; this particular yellow dragon may be based off the Amphisbaena, who is said to have been created along with various other serpents from the blood dripping out of Medusa's severed head.
Variants of NetHack often subject dragons to extensive changes, including the green dragon.
In the biodiversity patch, the yellow dragon is renamed to the guivre.
As with all other dragons in SLASH'EM, baby yellow dragons have a base level of 4 instead of 12, and can be encountered via random generation in ordinary levels with a frequency of 2; they are also eligible for creation on many levels that generate random D on level creation. Adult yellow dragons have a base level of 18 instead of 15.
Baby yellow dragons hit as a +1 weapon, and adult yellow dragons hit as a +3 weapon. Adult yellow dragons will not turn traitor while tame.
In the West the dragon was the natural enemy of man. Although preferring to live in bleak and desolate regions, whenever it was seen among men it left in its wake a trail of destruction and disease. Yet any attempt to slay this beast was a perilous undertaking. For the dragon's assailant had to contend not only with clouds of sulphurous fumes pouring from its fire breathing nostrils, but also with the thrashings of its tail, the most deadly part of its serpent-like body.
"One whom the dragons will speak with," he said, "that is a dragonlord, or at least that is the center of the matter. It's not a trick of mastering the dragons, as most people think. Dragons have no masters. The question is always the same, with a dragon: will he talk to you or will he eat you? If you can count upon his doing the former, and not doing the latter, why then you're a dragonlord."