The Keylekid were a hostile race of reptilian xenos that were ultimately wiped out during the early years of the Great Crusade by the Luna Wolves Space Marine Legion. The war against the Keylekid proved to be a long, brutal and miserable campaign for the XVI Legion.
Early in the Great Crusade the Luna Wolves encountered the hostile alien reptilian race known as the Keylekid on the world of Keylek. The grotesque Keylekid were greatly skilled in the arts of combat, and rose against the XVI Legion angrily the moment the 63rd Expeditionary Fleet made contact. Their world was a harsh place of crimson rock and indigo water. Horus, then known by his Astartes only as "The Commander" as it would be many years before he was named the Warmaster of the Imperium, expected a prolonged and brutal struggle, for the Keylekid were large and powerfully-built creatures. Even the least of their warriors took three or four Bolter rounds to bring down.
Yet, while the the Luna Wolves had come to their world to make war, at first the Keylekid would not fight them. The Luna Wolves did not comprehend the rules that these aliens fought by. The Luna Wolves learned later that the Keylekid considered war to be the most abhorrent activity a sentient race could indulge in, so they set upon it tight controls and restrictions. There were large structures upon the surface of their world, rectangular fields many kilometres in dimension, covered with high, flat roofs and open at the sides. The Luna Wolves named these structures "slaughterhouses," and there was one every few hundred kilometres. The Keylekid would only fight at these places, which were reserved solely for combat. War was forbidden on any other part of their world’s surface. They waited for the Astartes to meet them at a slaughterhouse and decide the matter. But the Luna Wolves destroyed them outright.
There had been suggestions within the XVI Legion to fight the Keylekid according to their own rules. Some Luna Wolves believed that there would be honour in such a gesture, but it was ultimately determined by Horus that the Space Marine Legions had their own rules which the enemy chose not to recognise. Besides, the Keylekid were a formidable species, and had the Luna Wolves not acted decisively, these xenos would have remained a threat to the Great Crusade and the larger Imperium. Horus also reasoned that it was clear that the Keylekid were a rigid species who would take a long time to learn new rules or to abandon their old ones, and thus were unlikely to be candidates for the acceptance of peaceful coexistence with the expanding Imperium. As a result, the Luna Wolves unleashed a campaign of xenocide that saw the Keylekid species wiped out when they refused to fight the Luna Wolves invaders outside of their prescribed places.
A preserved cadaver of a Keylekid warrior was later displayed in the Vengeful Spirit's Museum of Conquest.
- Horus Rising (Novel) by Dan Abnett, pp. 147-148