The creature known as Moonclaw was not born of mortal creatures, but instead hurled from the pale belly of Morrslieb when it was at its most bloated. Though at first glance he could be mistaken for a particularly hideous Beastman, Moonclaw is not of this world. For Moonclaw is utterly and irrevocably insane, his actions as random as they are lethal.
Upon the Geheimnisnacht when Moonclaw came unto the world, Morrslieb hung low and full in the firmament like the belly of a pregnant hag. The forests resounded to the orgiastic feasting of the Beastmen tribes. At the stroke of the witching hour, a blazing, horned comet seared across the skies. It briefly traced a green scar across the heavens before hammering through the clouds and slamming into the sacred grove at the base of the Barren Hills. A wave of green-black force flattened the forest for miles around. Nothing survived the disastrous impact save Moonclaw himself, who stepped steaming from the cracked remains of an egg-shaped lump of purest warpstone, his glistening fur slicked to his body by nameless fluids. Thus did Moonclaw step from the wyrdling substance of his lunar mother into the Old World.
Since that day Moonclaw has wandered the lands in a daze, speaking glottal syllables in a backwards tongue. His glowing, goat-slit eyes seem to see into another realm, and his erratic gestures leave doppelganger traces in the air. Wherever the Beastmen witness the lambent green-black flames that lick around Moonclaw they fall to their knees in worship.
When Morrslieb is nearest the earth, Moonclaw's power waxes full. It is then that Moonclaw summons the strange two-headed beast, Umbralok, that serves as his steed, and rides at the head of a great army. On these nights he seeks out the waystones that dot the Old World, edifices older than the race of man. Moonclaw desires nothing so much as to see these flung down and defiled so that the dark power they stem may flow out into the world. So it is that Moonclaw leads his followers against the civilised races, his twisted and mutated form crackling with barely contained power atop his fiendish steed. Few can tolerate the wave of madness that precedes Moonclaw on these most eldritch of nights, let alone stand resolute when jagged shards of lunar rock hurtle out of the skies to annihilate any who earn Moonclaw's displeasure.