She possesses the breath attacks of all of the other types of dragon as well as their resistances (including reflection and magic resistance!). Her corpse will randomly grant one which can be acquired intrinsically when eaten. She is a spellcaster.
The Chromatic Dragon is located in a large, open, hexagonally shaped level (see the caveman quest), and always starts out sleeping. The room also contains shriekers, which may wake her up. She respects Elbereth and like most quest nemeses, teleports to the up staircase when wounded. Typical strategy involves burning Elbereth onto the upstairs (or just engraving with whatever and levitate over it), and standing on it while fighting her. She will then stay next to you, casting spells but neither attacking physically nor using her fearsome breath weapons, and you can beat on her until she expires. (Shaman Karnov's advice, to "keep moving" when fighting the dragon, is in fact really really bad: stepping away from her exposes you to disintegration breath. No wonder they need your help.)
Because the Chromatic Dragon starts out sleeping, you will need to wake her up. In general you will not want to approach her, as attacking to wake her up may cause her to teleport to the stairs, where she can summon nasties to surround you with, causing much aggravation. Ordinary methods of waking monsters, such as beating a drum or throwing something at her are advised. You can hope for one of the shriekers on the level to shriek, causing her to wake up. If any of these methods can be done from the upstairs, this is advisable, as she will teleport to your position immediately. If you can bring a pet into the lair, it may attack the Chromatic Dragon for you while you wait on the upstairs.
The Chromatic Dragon is a spellcaster, so it is optimal to obtain magic resistance before facing her. She can curse the player's inventory and disintegrate random pieces of armor with spells (and whether or not you have magic resistance, she can always summon nasties). Reflection is highly desirable as well, as she possesses all breath attacks, including the disintegration breath of the black dragon. Of course, in the world of NetHack, obtaining these attributes can be easier said than done. Magic resistance can be foregone if you are confident you will be able to remain standing on an Elbereth, as this will negate most of her attack spells. Facing the chromatic dragon without reflection can be frightening, but she will not breathe on you if she is next to you, and can not if she is not in a straight line along one of the eight aiming directions in NetHack. So if you engrave on the stairs, wake her with a loud noise, and never leave the stairs, you hopefully will not get disintegrated! A risk, but one you may be willing to take for the prize of the Sceptre of Might, a splendid melee weapon that also conveys magic resistance.
UnNetHack renames this quest nemesis to Tiamat and includes the possibility of encountering generic Chromatic Dragons in the Dragon Caves, whose death can produce scales (and thus armor) which are resistant to multiple types of attacks (this new armor provides reflection and fire, cold, sleep, disintegration, shock, poison, acid and stone resistance).
Tiamat is an important Dungeons and Dragons monster. She has five heads, corresponding to five color dragons (black, blue, green, red, white) with their corresponding powers. Her body is a blending of various color dragon forms with an appropriately multicolored hide. The tip of her tail has a poisonous stinger.
Her name comes from a Babylonian god, other wise, unrelated to the D&D Tiamat.
Encyclopedia entryShe is referred to as Tiamat in the Encyclopedia.
Tiamat is said to be the mother of evil dragonkind. She is