Chaos Beast
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Chaos Beasts are a catch-all term for any critters living in the Warp. They differ from deity-aligned daemons as they are born from the raw emotions of the Warp itself rather than a splinter of a Chaos God. They are often native to Daemon Worlds and act as the local fauna and flora. These creatures come in many forms, but each is a creature of muscle, fangs, and claws, with only the thought of carnage driving it.
Many of these beasts are often captured by Traitor Marines and use as either gladiatorial matches or as glorified zoo animals for all the little Chaos children to look at. It has been rumored that the Great Beasts of Caliban are but another variation of the Chaos Beasts. Although telling the Dark Angels that their Primarch is somewhat related to the Chaos Beasts due to one of his nicknames being, you know, The Last Great Beast of Caliban, would probably be the quickest way in getting your ass purged other than being the Fallen WHAT!? OUR PRIMARCH EARNED THAT NICKNAME DUE TO HIS HEROIC WRATH AGAINST THE ENEMIES OF MANKIND! THERE ARE NO SUCH THING AS THE GREAT BEASTS NOR THE FALLEN! THEY ARE JUST FAIRY TALES WE TELL TO OUR CHILDREN YES! TO EQUATE HIM TO THE LOWEST CHAOS MONGREL IS HERESY! still doesn't explain why he calls himself a beast if he is a man of honor and valor THE LION IS A NOBLE BEAST! REPENT MOTHERFUCKER!.
Anyways, sometimes Chaos Beasts are hunted and tamed as warbeasts by the Dark Eldar. What, where do you think they got all the Khymerae from? Your local Imperial pet shop?