The ki-rin, A, is an angelic being in NetHack. It is often a candidate for a player's steed (if they manage to tame one - difficult due to its high magic resistance, making a wish for a figurine a more likely method) due to its high speed, power, and ability to fly. A ki-rin steed will never buck you because of conflict due to its high combined base level and monster magic resistance unless it is level drained below 15.
A ki-rin makes a superb steed for players that spend a lot of time riding. It is the only steed with a faster-than-normal movement rate that can fly. Because ki-rin are spellcasters, they will cast haste self, giving them an effective movement rate of 24, making them as fast as a non-fast warhorse or unicorn. Perhaps more importantly, their high hit points, damaging attacks, ability to heal self, and high magic resistance make them powerful enough to survive in Gehennom.
Once you have mounted a ki-rin, you should not dismount unless absolutely necessary. Since only knights start with riding skill at basic, other roles will not be able to pick up objects, #loot containers, drop items on altars, #dip items in fountains, etc. initially. Because a ki-rin will go feral after five mount attempts, it is better to advance riding skill on a more traditional mount such as a horse first, then switch to your ki-rin once you reach basic skill. Roles which are restricted in riding will probably not have much use for them.
Prior to NetHack 3.6.0, ki-rin were able to wear amulets, boots, shields, and gloves despite being ridable. This was bug C341-18. Variants based on 3.4.3 that did not address this bug themselves will allow a ki-rin to wear additional equipment, including obtaining reflection from an amulet or shield.
In addition to all the benefits above, ki-rin in SLASH'EM require a +3 weapon to hit. This makes them better steeds: they are immune to most physical attacks, including powerful minotaurs and even some Demon Princes; it also makes them more dangerous should you encounter a hostile one. Note that ki-rin are not level-drain or stoning resistant, so an amulet of drain resistance or an amulet versus stone are also good options for the amulet slot. Ki-rin are also given as minions to lawful players, starting at level 13, though minions cannot be saddled or ridden.
The Ki-rin originates from Chinese mythology, and it is considered benevolent. It resembles a horse/deer-shaped Asian dragon (this includes deer-like horns).
The more frequent romanised name is "qilin".
The ki-rin is a strange-looking flying creature. It has
scales, a mane like a lion, a tail, hooves, and a horn. It
is brightly colored, and can usually be found flying in the
sky looking for good deeds to reward.