Sigmaron is a great palace city in the Realm of Azyr dedicated to Sigmar. Mallus, the core of the World That Was, and Mannslieb, the white sphere that was one of the World That Was' two moons, hang above it.
Mallus is mined for sigmarite that is used to forge the wargear of the Stormcast Eternals.[1]
The remnants of the Free Men live in Sigmaron.[2][3]