| Category | Worlds |
| System | Mechanus |
| Domain | Planning |
| Formed | Lost Ages |
Regulus is a remnant of the Lost Ages, an artificial realm that once constructed colossal machines. In the Dawn Era, 751 DE, Regulus was extracted from the Sea of Entropy, becoming the foundation of the Mechanus System.
On the world of Bal-Kriav, two features were originally from Regulus. In 4261 DE, the Master of Tides was slain while attempting to consume Regulus. During this assault, a fragment of the world was torn free, named the Ebon Bedrock, which eventually found its way to Bal-Kriav. In 1482, a colossal clockwork gear, the Gear Monument, plummeted into the Great Expanse.
The largest city of Regulus is the Modron city of Ancoph-Glycern. This grand, gear-filled metropolis is in truth two cities that expanded to such a tremendous size they ultimately coalesced into a single entity.