Morrslieb is the Old World's second moon, and the wrong one. Where its fair sibling Mannslieb waxes and wanes in orderly fashion, Morrslieb is a sickly green orb that wanders the sky on no course astronomers can chart, swelling and shrinking as it pleases and sometimes, observers swear, leering down like a face. Scholars who keep their theories quiet hold that it was born when the ancient polar gates collapsed into the Chaos Wastes, and that the moon is a mass of solidified Chaos — perhaps pure warpstone, the crystallised dark magic that mutates whatever it touches.
Its influence argues for the theory. When Morrslieb rides full, the Winds of Magic blow strong and strange, mutations bloom among man and beast, and the beastmen of the deep forests gather howling at their herdstones. From time to time fragments fall from it as green meteors: one such warpstone rain is blamed for the cursed soil of Sylvania, and prospectors who dig for fallen shards rarely live to enjoy the price they fetch.
Worst of all is Geheimnisnacht, the Night of Mystery, when Morrslieb hangs full and monstrously close. Across the Empire doors are barred, witch hunters ride, dark covens gather, and sensible folk pray to Sigmar until sunrise.