The Fabricator Locum is the second highest-ranking individual on the planet of Mars and other Forge Worlds. The Fabricator Locum assists the Fabricator General with the governance of Mars, including the meeting of production quotas and ensuring the correct devotions to the Machine God are observed at all times. The most notable Fabricator Locum was named Kane. He sided with the Emperor of Mankind during the Horus Heresy and thus maintained at least some crucial Mechanicus support for the Loyalists.