Archons are the most powerful of the angelic beings and, indeed, possess the second highest difficulty level of all randomly generated monsters (next to the arch-lich). They are exceedingly popular as pets due to their power (and as pets cannot cast attack spells, the arch-lich is far less desirable as a pet due to its weak cold attack and complete lack of other physical attacks).
Archons have such high difficulty that even for a level 30 character they cannot appear before dungeon level 22. Since the Dungeons of Doom end at or before level 29 and Archons cannot be generated in Gehennom, most characters will not see one before finding the Amulet of Yendor. Once you have the Amulet, your effective dungeon level is at least 45, so Archons may be randomly generated from the Castle up. There are no guaranteed Archons in the game. There is one exception to these rules - the random A generated on the second version of Medusa's Island could theoretically be an Archon, but it is quite unlikely.
The best way to fight Archons is to use a cockatrice/chickatrice corpse and be blinded to protect yourself from the stunning and blinding effects of their gaze. Wearing the Eyes of the Overworld also prevents you from being stunned or blinded by this attack. Archons' guaranteed shield will reflect a death ray (or any other ray, for that matter), but Vorpal Blade can decapitate them. They are too large to be bisected.
Another option is to try avoiding them and keep moving. Their inability to unlock doors can help. Archons will always be peaceful for lawful characters of non-negative alignment. Some players consider this a significant advantage of being lawful.
Excessive use of genocide may lead to an "Archonstorm", a scenario in which overwhelming numbers of Archons begin to appear in the endgame, in place of other high-level monsters that have been genocided. Neutral and chaotic players can keep the chances of such a scenario low by using genocide sparingly. (Lawful humans will probably want to use moderation in using genocide as well, due to the -1 alignment penalty associated with it.)
Archons as pets
As mentioned above, Archons make outstanding pets. They are fast, use their blinding gaze (monsters don't get stunned by this attack), hit hard and wear armor. A level 25 or higher Archon will always ignore conflict. A level 32 or higher Archon will also be immune to polymorph traps (but not levelporters). The easiest way to get a pet Archon is to apply a blessed figurine of an Archon. It is possible for a high level character to tame an Archon with a spell of charm monster but it may require a number of attempts. The Castle is the most promising place to farm for one once your level is high enough, but Vlad's Tower might also do.
Archons will wear gloves, helmets, boots and shields but they're too large to wear any armor that fits on the body. To get a pet Archon to wear armor, enchant the piece of armor and then drop it in front of the Archon. Archons will also pick up and use a variety of items, including unicorn horns, amulets of life saving and potions of gain level.
Archons will wield weapons left for them but getting them to drop their starting weapon can be difficult. Applying a bullwhip towards them can strip them of their current weapon, allowing you to hand them another weapon or simply giving you the opportunity to enchant their starting one before handing it back. If you give your pet an artifact while it is carrying nothing else, it will never unwield it: monsters prefer (non-cross-aligned) artifact weapons over everything else, and rank those they have by position in an internal list.
In SLASH'EM, because the dungeon is much deeper, there is a higher probability you'll encounter them before the castle. Solars make even better pets.
Archons in dNethack are now split into 7 varieties. The counterpart to the vanilla Archon is a Throne Archon. In addition, as the #loot command can now take items from pets, it's much easier to remove Sunsword or Demonbane from a pet. You can also use this to give them a different artifact/non-artifact enchanted weapon, and take Sunsword for yourself.
Archon is Greek (ἄρχων arkhon) for "ruler" or "lord". It refers to ancient Greek "ruling gods".
Archons are the predominant inhabitants of the heavens.
However unusual their appearance, they are not generally
evil. They are beings at peace with themselves and their
- makemon.c in NetHack 3.4.3, line 268: the game always tries to give overlord A's one of the two artifacts; if the chosen artifact has already been generated, it will be converted to a normal rustproof long sword. Thus, when one of the two artifacts has already been generated, the next Archon generated has a 50% chance of receiving the other.
- makemon.c in NetHack 3.4.3, line 1318