The worlds of the Imperium are categorised according to a staggering range of factors, but can be divided into the loosely-defined groupings listed here. Most Space Marine Chapters maintain their fortress-monastery on the same world they recruit from, but this is not always the case. While the Space Wolves recruit exclusively from Fenris, for example, where they also maintain their fortress-monastery called The Fang, the Crimson Fists reside on the Civilised World of Rynn's World but recruit from other planets in the region.