The native Human population inhabit the plains and riverside, the former being the range of Nomadic hunters and herdsmen who trade with and prey upon the settled agriculturalists of river, fen and lakeside. The canyons and caves of the mountain massif and the ruins of the ancient cities are the lurking grounds of bands of mutants. Three major Mechanicus settlements have been established on Saka, in the Ferrea Mountains, the Celsae Mountains and the Lorica Mountains, to exploit the riches of archaeotech to be found in the ancient cities. The fortress monastery of the Lightning Chapter, Fulminis Instar, stands on an eminence overlooking the broad Valle Fulgoris.