It has the soft, sticky and mottled body of a pallid slug, webbed feet that flap uselessly, a face of writhing green tentacles, and a whip-tail growth that bursts from its back and which wags constantly from side to side.
The essence of mindless decay and horrid rot given putrid flesh, Beasts of Nurgle exemplify the Plaguelord's endless enthusiasm and excitement for forces of life and death. Thus, a Beast delights in discovering new things and making (to its very simple mind) new friends.
When brought into realspace they act almost akin to a curious and inquisitive pet, investigating anything and everything in sight, and spreading illness and rot wherever they go.
Immense slug-like monstrosities, Beasts of Nurgle crawl across the ground on their bellies, weakly propelled by clawed flippers, leaving a layer of stinking slime in their wake.
While slow, the Beast is implacable in its advance, undeterred by all but the most fearsome of weapons, as relentless as the decay it embodies. Each is a nightmarish conglomeration of parts, with a lengthy neck holding a wide-eyed face of almost blissful idiocy.
The gaping tooth-filled mouth houses a lolling tongue dripping with putrid saliva. Clusters of writhing tubes sprout from the Beast's neck and back, each one spewing forth swarms of buzzing flies, clouds of vomit-inducing gases, flesh-eating fluids capable of finding gaps in even the most secure of armour, or other foul gifts.
The Beast of Nurgle is no less deadly than it is ugly, for its touch causes paralysis and its slimy secretions rot everything they cover. The very proximity of a Beast is sufficient to kill small animals and plants, and even larger creatures may age and decay perceptibly in its presence. Indeed, the Beast is the very embodiment of the universe's mindless decay.
Despite its fearsome appearance and deadly attributes, the Beast is an affectionate creature that behaves in all respects exactly like an over-friendly and easily excited puppy. It craves attention, greeting newcomers by slobbering all over them with its slimy tentacles.
Once they get thoroughly worked up they can rarely (if ever) contain themselves and leave little piles of acrid slime in their wake. All this attention is not a problem to other creatures and servants of Nurgle, but tends to kill mortals fairly rapidly.
Unlike most Daemons, a Beast kills not with rending claws and ripping teeth, but with a strange form of kindness. Victims are caressed, petted, and stroked with the Daemon's multiple tentacles, while the long tongue delivers slobbery and slimy licks.
In very short order, the victim is sickened, infected, dissolved, and then crushed, ground under the Beast’s vast bulk. The Beast, for its part, feels a touch of sadness at the inability of its now-dead friend to join in on the merriment, but quickly forgets about him as something (or someone) new attracts its attention.
Once the Beast's new friend stops moving, its interest quickly shifts to another target, and in this way the creature excitedly and lovingly poisons and kills just about everything it touches. As the Beast has only the most rudimentary sense of intelligence it never anticipates the result of its boisterous behaviour, and registers only a slight sense of disappointment as each new friend goes still and boring.
When they manifest in battle alongside the Heretic Astartes of the Death Guard Traitor Legion, Beasts of Nurgle are cynically exploited as line-breaking units. The Death Guard have little time for the Beasts' attentions, and no more desire than most to be crushed under their galumphing weight.
Thus they herd the Beasts toward the enemy as best they can, often baiting the creatures with speeding tanks -- which they delight in chasing -- or bands of hapless Chaos Cultists. Should the Beasts be torn apart by heavy fire, those shells are at least not falling upon valuable Death Guard warriors. If the Beasts of Nurgle successfully punch a hole in the enemy lines, Mortarion's sons waste no time in exploiting their advantage.
A prime example of the destructive power of a Beast of Nurgle can be found on the Agri-world of Gabali III in Winterscale's Realm in the Koronus Expanse. There the province of Gevaudan suffered hundreds of casualties as a Beast wandered about the farm fields, destroying crops, herd animals, and buildings.
Seemingly unstoppable, it took the combined efforts of Enforcers and local planetary militia units to finally destroy the Daemon. Even after death, however, its presence lingered, as crops grew sickly and many fields had to be torched to the bedrock to remove the diseased corruption.
Another example was when the Death Guard used Beasts of Nurgle at the Third Battle for Tarran's Pass. When the Scourge Stars arose, Death Guard vectoriums launched strikes against nearby worlds, ensuring that no enemy was in a position to disrupt Mortarion's muster for the invasion of Ultramar in the Plague Wars to come.
On the planet of Daxar, the Apostles of Contagion met stiff resistance from an Astra Militarum force built around the 56th Cadian Heavy Infantry. Though the Death Guard drove the Cadians back from the defences of Haldyon City before harrying them across the sulphur deserts beyond, at the mouth of Tarran's Pass the Imperial Guard dug in and resisted all conventional attacks.
Conscious that his enemies were mustering their reserves for a concerted counterstrike, and that the will remained upon Daxar to disrupt Mortarion's plans, Death Guard Lord Thelugh Poxmaw commanded that a mighty summoning ritual be performed. As dark clouds spiralled overhead and the moons crawled backwards in the sky, several hundred Beasts of Nurgle were conjured into being and sent gambolling towards the Imperial defence lines.
Dozens were blown apart by Cadian fire, dozens more hacked and blasted apart at close range, but the remaining Beasts ploughed on regardless, and the depleted Death Guard followed in their wake. With the barricades smashed, the pass ran red with Imperial blood, and Daxar fell soon after.
Rot Fly Origins
Though few know the truth, the putrid daemonic creatures known as Rot Flies are, in fact, metamorphosed forms of Beasts of Nurgle who have given in to spite and despair.
Over thousands of Terran years, even the simple joy of Beasts of Nurgle can be soured by their playmates' unwillingness. A seed of discontentment takes hold within some, a canker of bitterness and disillusionment that grows with every fresh rejection.
Should such a doubting Beast be slain and banished back to Nurgle's Garden in the Realm of Chaos, it will slump into the muck and filth with a resigned sigh and give in to its misery.
Eventually they are cocooned by a cloud of Nurgle's fattest flies, and when they finally emerge, a bloated Rot Fly rips its way free, fully formed and driven by all the hate and cruelty that soured the Beast of Nurgle's simple heart.
- Codex: Chaos Daemons (6th Edition), pg. 48
- Codex: Chaos Daemons (4th Edition), pg. 38
- Codex Heretic Astartes - Death Guard (8th Edition), pp. 54-55, 83
- Rogue Trader: Koronus Bestiary (RPG), pg. 118