I love the two different fluff pieces:
The Carnodon is a versatile medium battle tank which acted as the lynchpin for many of the storied successes of the Imperial Army during the Great Crusade. As a premier mobile fire platform, it was regularly adapted to combat a wide variety of foes and respond to any number of battlefield conditions. At Gamma-Incunablar, a squadron of the 43rd Veradan’s Carnodons, fitted with las weaponry, brought down the first of the great Basemekanic beasts which had subjugated that world, their concentrated firepower surpassing even the Predator tanks of the IIIrd Legion to punch through the vast creature’s thick metallic hide. On Hektun, the 3rd Saturnyne Rams earned their reputation as the ‘Incinerators’ of the Solar Auxilia when their Carnodons, fitted entirely with volkite weaponry, were used to strategically ignite the hydrogen-rich vents of the Phenaem’s tunnel structures, eradicating the foul xenos within.
The Carnodon tank was foremost of many initiatives undertaken by the Imperial Host to exploit the modular design of the relatively new Aurox chassis during the expansion of the Imperium by creating variants based on it. During the early years of the Great Crusade, it rapidly became a byword for conquest amongst the Expeditionary fleets, a legacy which led to the production of the dedicated Imperial battle tanks of latter-days. As the Great Crusade moved ever outwards and supply of the Aurox chassis peaked, it is thought that many Carnodon tanks entered a strategic reserve and were distributed to Crusade muster worlds behind the front lines; with over two hundred thousand examples thought to have been stored pending secondary mobilisation in the warrens under the world of Tallarn
Hailing from the prehistory of the Imperium, the Carnodon tank is a true relic of war. Those few that have survived the passage of the millennia are revered as links to the former incarnation of the Astra Militarum – that mainstay of the Great Crusade, the Imperial Army. With the hour so dark, and the need for trusted war assets greater than ever, the Priesthood of Mars has reinstated the STC for the Carnodon on several forge worlds, and under the light of the Great Rift the ancient tank has trundled forth from their manufactorums once more. Bristling with multi-lasers, the Carnodon is an ideal tool for mowing down elite infantry, blasting apart transports and crippling light tanks – it is respected as a fearsome asset for any armoured regiment. Carnodons are capable of mounting almost any heavy weapon in the Astra Militarum’s arsenal – more than that, they have the power-rich infrastructure and fiery machine spirits needed to carry the little-understood volkite weaponry. Even those foes that cannot be laid low by high-intensity lasers will be reduced to ashes by the deflagratory fires of a volkite beam.