From 1d4chan
No, they are not safe to pet. Any attempt to do so may result in your entire arm being nommed.
Definitely not Santa's little helper.

Khymerae or Khymera (Seriously Games Workshop, is it so hard to just call them Chimeras?) - Panthera somnium - are what happens when the Dark Eldar decides to go a little bit of field hunting inside the Warp. Yeah you heard that right, Khymerae are beasts from the same place where the guy with anger management issues, the schizophrenic giant blue bird, the personification of all neckbeards and the cock-humping chick on cocaine with a fetish/appetite for Eldar souls all live in. How the Dark Eldar manage to tame these without having their souls eaten is a mystery.

Khymerae are literally born from a person’s nightmares and like all creatures from the Warp, no two Khymerae are the same. For some reason, taxonomists of the Ordo Malleus classify them not as actual daemons but as warp creatures, one example of the many unnatural flora and fauna existing in the Immaterium, though this distinction is usually lost on those facing the beasts. Khymerae are also known to phase into things, what with being from the Warp and all. This means that Khymerae have all the possibilities to appear inside of moving void ships despite the fact that the ships have their Gellar Fields on, but alas Warp shenanigans trumps all explanation.

They grow like cysts on the night terrors of the Dark Eldars' slaves and are dragged into reality and tamed or something.

While each Khymera is distinct, they all follow the same body pattern. In this case every single Khymera looks like a skinless feline with the skull of a snake, tentacle-shaped whips of serrated flesh or boned skeletal scythes, at least two smaller talons which are found on the chest and multiple eyes. Essentially speaking, they are fucking ugly adorable Warp-zerglings.

They are pack hunters and are often grouped in several members. Dark Eldar Beastmasters are quite fond of them, as you can imagine, with their whole "Terror is my wine and fear is my meat" shtick. They then enslave them as half-real nightmares that can wreak utter havoc upon a battlefield before fading away like mist.

On tabletop, these little beasties are decent harassers with a 5++. Basic stat line of a marine but much cheaper and 3 cc attack, able fill up small hole in your deployment zone to deny alpha attempt.

Forces of the Dark Eldar
Command: Archons - Haemonculi - Kabalite Trueborn
Lhamaeans - Medusae - Sslyth - Succubi
Troops: Beastmasters - Commorragh Slaves - Grotesques
Hellions - Incubi - Kabalite Warriors - Mandrakes
Scourges - Wracks - Wyches
Beasts: Clawed Fiend - Khymerae - Razorwing Flock - Ur-Ghul
Pain Engines: Cronos Parasite Engines - Talos Pain Engines
Vehicles: Raider - Ravager - Reaper - Reaver Jetbike - Venom
Flyers: Raven Fighter - Razorwing Jetfighter
Voidraven Bomber
Spacecraft: Impaler Assault Module - Raptor Fighter
Slavebringer Assault Boat
Super Heavies: Tantalus
Auxiliaries: Harlequins