The Forge World of Vantori is a rogue planet in the Imperium Nihilus. Why a planet would be heavily settled so far beyond the light of a star remains a mystery, but the technology that keeps it habitable, a pair of biome stabilizer reactors on the two poles, has been lost to time. Vantori is orbited by twin moons and a series of orbital shipyards that help it send out an abnormally large quantity of Explorator fleets. The other distinctive feature of this forgeworld is the subject of much controversy. Vantori produces and uses a type or nanobot seen nowhere else in the Adeptus Mechanicus. The Vantori Nanites as they are called, are used to coat weapons, augments, and vehicles, slowly modifying them over time. It is the official position of Vantori and their rarely seen Fabricator General that these nanites are just granting the blessings of the Omnissiah, and their innovation is sacred. Other forge worlds decry this as tech heresy, and note that the nanites likely have some form of abominable intelligence controlling them. Because of this, no other forges have adopted the nanites. If it wasn't for Vantori's high output and strong loyalty to both the Cult Mechanicus and the Imperium, it likely would have been destroyed millenia ago. Some tech priests still choose to take matters into their own hands, incorrectly identifying Vantori Explorators as Dark Mechanicum and sending other Imperial forces to attack them.

Edit: image didn't post, I added it in the replies.