Mezoa

Mezoa is a volcanic Gothic Sector forge that Ferrus Manus and the Emperor helped raise from Lucius stock, and it never hosted a Titan legion because the cooled lava would not take the weight. It told Horus's envoy Regulus to get lost, then survived the Mezoan Campaign in 008.M31 when Cassian Dracos and a scratch loyalist host broke Iron Warriors and Alpha Legion on the crust. The Path of the Flame Eternal still marks its cult as odd even by Mechanicus standards.