The primary (and natural) moon of Warhammer Fantasy. It's name is a reference to the human god of the seas, Manann due to the effect it has on tides. It's presumably a fairly normal sphere of rock and regolith. It is associated with many different gods, primarily among them being the High Elf god Lileath. When it's unnatural twin, Morrslieb eclipses it, you're in for one wild night. More specifically Geheimnisnacht and Hexensnacht, Halloween and New Years Eve respectfully.
Mannslieb miraculously survived the End Times completely unharmed. Though, to be fair, after the destruction of the World that Was into space debree, Mannslieb is basically just a big rock floating into space, probably getting pummeled by all the remains of the old world.
Sigmar built a giant lampost beneath it to illuminate the new home of humanity, Azyr/Sigmar/Whateverheim.