The Proteus Land Raider was an ancient and revered pattern of the Legiones Astartes' most iconic armoured transport, predating the more common Phobos variant that would dominate the later Imperium. Distinguished by its explorator augury arrays and heavier reliance on twin-linked lascannon sponsons, the Proteus served both as an assault vehicle and as a deep-strike reconnaissance platform during the Great Crusade and the Horus Heresy.
Its machine spirit was famed for its resilience, and the pattern's ability to mount specialised sensor equipment made it invaluable for spearhead operations into uncharted or hostile territory. Because relatively few remained in service by the time of the Heresy, a Proteus was often entrusted to a Legion's most elite formations and Terminator elites.
Legions with long crusade histories, such as the Dark Angels, retained numbers of these venerable machines, while the Imperial Fists employed them to breach fortified enemy positions. Maintained through the ministrations of the Mechanicum, the Proteus embodied the martial heritage of the First Legions and their unbroken armoured traditions.