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.
Mannslieb miraclously survived the End Times completely unharmed. Sigmar built a giant lampost on top of it to illuminate the new home of humanity, Azyr/Sigmar/Whateverheim.