Tartaros Terminator armour was a refined pattern of Tactical Dreadnought plate developed late in the Great Crusade, prized for combining the resilience of Terminator armour with a freedom of movement its heavier cousins lacked. Where the older Cataphractii pattern rendered its wearer a slow-moving fortress, Tartaros plate allowed something closer to the agility of standard power armour while retaining the fearsome protection that defined its class.
The secret lay in an advanced power distribution and a more elegant construction, the fruit of Mechanicum artifice at the height of its craft. A legionary so armoured could keep pace with an assault, wield the heaviest weapons, and still weather storms of fire, making Tartaros suits favoured among veterans who valued mobility as much as endurance.
Such armour was rare and costly, issued only to the most honoured warriors of a Legion's inner cadres. Like all Terminator plate, its patterns would grow steadily more precious as the Age of Darkness consumed the forge-worlds and scattered the knowledge of their making. In the long twilight that followed, a suit of Tartaros armour was a relic worth a company of lesser wargear.