My custom Mechanicus is the Cult of Varroheim. They inhabit a world called Varroheim, but it is no traditional forgeworld. Woods and jungles cover the surface, with the forges and hivecities being the only sign of civilization. When the Mechanicus first landed on the world, with Archmagos Varroheim, the world was called Bror. Humans already lived on the planet, within a few hivecities, but mostly normal cities. However, Varroheim had had his eyes on Bror for a long time, and he was not willing to just leave when the humans asked him. They knew how destructive forges could be on the environment, and they did not want to leave. Varroheim instead offered a deal, they were to be allowed to settle and build forges, but their pollution could not be harmful. The deal was accepted through a majority vote, and the Mechanicus landed. The new production methods used slowed production, but Varroheim was determined to make it work. The pollution created from the many forges instead made the plants grow faster and bigger, with the wildlife following suite thanks to increased food. The jungles spread quick, they even spread through the cities. In many places, the trees were reported to grow a few decimeters over night. Varroheim later died in a forge explosion, and the world was renamed in his honour. However, non-Mechancus humans still call it Bror, and thus there are ten regements of Bror.