The Magma Hounds are a warband of Chaos Space Marines. They were once a Loyalist Chapter of Space Marines of unknown origin and Founding, known as the Knights Excelsior. They were corrupted after entering the Eye of Terror in 321.M37 as part of the Imperial Abyssal Crusade. During their sojourn in the Eye, the Knights Excelsior found themselves on the Dark Forge World of Temporia, home of the vile Heretek and Warpsmith named Valadrak. While investigating the strange artificially-constructed world composed of endless manufactoria and machines, they were attacked by strange, living Daemon Engines.
Outgunned, the Knights Excelsior were forced to make a hasty tactical withdrawal, fighting their way back to their dropships. As the Chapter attempted to make good their escape, their orbiting warships were attacked by a strange archeotech device that rendered their technology impotent, leaving the Space Marines at the mercy of Temporia's Daemon Engines. When the Knights Excelsior were last seen, they had been refashioned into the Renegade Magma Hounds.
The Magma Hounds were a formerly Loyalist Chapter known as the Knights Excelsior. Following the Ecclesiarchal Purges of 321.M37, a dozen star systems were engulfed by Warp Storm Dionys, its echoes rippling along the spiral arms of the galaxy as it raged through the Empyrean. Records of mutation and Chaos Cultist activity quadrupled overnight. Worse yet, it was not only the citizens who were affected by the sudden influx of Chaos. Many of the Space Marine Chapters with homeworlds affected by the Warp Storm found that the secret imperfections in their gene-seed were writ large upon their new recruits, giving rise to a wave of disturbing manifestations both physical and psychological. The Knights Excelsior were one such Loyalist Chapter of Astartes that had been affected by these Warp Storms.
When the Ecclesiarchy heard of this sinister tum of events, Saint Basillius the Elder demanded that all those Chapters of the Adeptus Astartes whose homeworlds had been touched by the Warp Storm be rendered unto his judgement. Such was the elder's influence with the High Lords of Terra that within a standard year this had come to pass. After a series of stringent tests and prognostications, hundreds of Chapters were deemed unaffected by the Warp Storm. No less than thirty were found wanting. The Judged, as these fallen Chapters came to be known, volunteered for a redemptive Penitent Crusade. The most militant of their number demanded the right to purify their tainted flesh in the fires of battle, to make a noble end from tragic misfortune. To the surprise of his closest advisors, Saint Basillius agreed to this proposal. He saw it fitting to send the accused into the Eye of Terror, taking the fight for the Imperium's future to the Daemon Worlds inhabited by the Traitor Marines.
A representative from each of the doomed Chapters held an emergency Council of Dismay to discuss the proposed Crusade. After scant hours of debate, they acquiesced to Basillius' demands, for they believed that martyrdom was preferable to an existence of suspicion and doubt. The last few days of 321.M37 saw a solemn procession of Strike Cruisers and Battle Barges pass through the Cadian Gate into the Eye of Terror, relay systems dormant and heraldic colours obscured by black mag-plates. One by one, the Chapters of The Judged disappeared into the iridescent dust nebulae that surrounded the Eye. As the massive Space Marine flotilla entered the Eye of Terror, they were set upon by a massive Chaos warfleet. The resultant battle was so fierce that the ships of The Judged were forced to retreat and were scattered to the furthest corners of the Eye.
Stranded across the Void Gathalamar, the Knights Excelsior fought desperately to make sense of their new environment. The Dark Forge World of Temporia was a mind-bending contradiction of cog-plateaus, helical manufactoria and spiralling stairways that clanked and span around the newcomers as if they were the epicentre of the world they had invaded. At first glance, the Knights thought the beasts that crested each of the towering buildings were no more than drake-headed gargoyles, but the creatures unfolded themselves from the spires and roofs and plummeted towards the Space Marines, their maw-mounted weapons spitting fire. Yet more Daemon Engines clattered from the sweltering forges of each cog-complex as red-hot lava rained upward towards the intruders in defiance of physical law. Covered in the oily blood of Daemon Engines, the Knights Excelsior hacked a path back to their dropships, but their escape was far from secure. The creator of the daemon-beasts, Warpsmith Valadrak, allowed the Knights to re-embark upon their Strike Cruisers before setting loose an electricity-eating daemon fashioned from tortured Machine Spirits. With the control of their dormant warships rebelling against them and their advanced wargear pulsing with static, the Space Marines were overrun, seized up in the piston-driven claws of Temporia's Daemon Engines and thrust into the red-hot soul-forges of Valadrak's fortress. Less than a Terran year later, the Renegade Magma Hounds were seen abroad in the Cadian System, their number almost double that of previous sightings.
The Magma Hounds warband colours are faded sangria red with faded gold trim and shoulder pauldron insets.
The Magma Hounds warband badge is a black, flaming canine skull centred on a field of faded gold.
- Codex Heretic Astartes - Chaos Space Marines (8th Edition), pg. 53
- Codex: Chaos Space Marines (6th Edition), pp. 17-19