Death Guard - The Great Crusade: In the solar decades that followed the renamed XIVth Legion fought tirelessly in the service of the Great Crusade, never relenting in battle beneath their Primarch's gaze they pursued the liberation of Mankind with a fervour the Great Crusade had never known.Their restless fleet ploughed the cold void from one campaign to the next, resupplying on the move, never pausing but to make war. The Death Guard did not garrison, they did not build, they only tore down and slew, coldly, determinedly and with the inexorable progress of a contagion or a tsunami wave, and worlds fell before them.Over time Mortarion shaped the creed and practice of the Death Guard, his beliefs in many ways forming a natural extension of their own, beliefs and doctrine becoming ever more refined and extreme. At the heart of them was the unshakeable determination that Mankind should be free of oppression and terror. Such freedom could only be won in the Primarch's mind by destroying those that would shackle and devour humanity.This was a war to be fought without mercy or limit, without restraint or relenting. The battle for the human future was one that could only be won by enduring any hardship, no matter how terrible, and not shirking from any act, no matter how savage in pursuit of victory. This single end, the liberation of humanity to Mortarion's creed, justified any means.Mortarion took command of his new army with proprietorial severity. Though he was cold and aloof towards his sons, they worshipped him unquestioningly, and followed his teachings to the letter. Mortarion saw in them an opportunity to continue his labours upon Barbarus.He would forge the Death Guard into perfect infantrymen, adaptable and self-reliant warriors who specialised in the use of durable weaponry that was easily maintained and re-supplied. The Death Guard were taught to choose the best ground, and then to grind their enemies down upon it with massed infantry formations.They were the anvil to their allies' hammers, or else the bludgeon that battered the foe into submission. Some amongst Mortarion's brother Primarchs disparaged his tactics as blunt and unimaginative; in truth, the doctrines of the Death Guard were durable and efficient, and demonstrated a remarkable talent for grass roots martial organisation that earned the Death Guard a truly impressive honour roll of victories during the Great Crusade.Mortarion's gene-seed made his sons hardy. Through his swiftly imposed regimens of toxin hardening and extreme environment tempering, the former Dusk Raiders became more durable than ever.This inherent toughness only increased, for Mortarion recruited the bulk of his new Legionaries from Barbarus. The Death Guard were rightly proud of their indomitable physiology. They deployed into the most hazardous war zones where even other Space Marines hesitated to tread, and made widespread use of rad and Phosphex Weapons, alongside proscribed viral agents that soon earned them something of a dark reputation amongst their brothers.Mortarion cared not for the distaste of his peers. His personal mission was the overthrowing of tyrants, beings such as the carrion lords of Barbarus, and he took pride that his sons could employ their own rugged strength to defend those too weak to protect themselves.Still, for all their achievements, the labours of the Death Guard went largely unrecognised. Mortarion was far closer to his brother Horus than to his sire the Emperor, believing that the former recognised his worth far better than the latter ever would.Worse, the longer they fought to shield the weak from oppression, the more the Death Guard became overly enamoured of their own fortitude, and dismissive of those too weak to protect themselves.