Machina

Short Version

The Machina is the cogitator containing the Machine Spirit of the Golden Throne.

Long Version

Long ago, only 3 years after the Emperor was interred in the Golden Throne, Rogal Dorn met with his surviving loyalist brothers. They argued that one of them had to stay with their father's body, to make sure nothing went wrong while they waited for him to recuperate. Meanwhile, recent attacks by some kind of hacker nearby worried the council that someone might accidentally (or on purpose) might tamper with the mechanisms of the Golden Throne further, potentially killing the Emperor. Eventually Dorn came up with the answer: package the machine spirit of the Golden Throne in a cogitator known as the Machina and connect it to the Palace on Terra by a quantum line, allowing the Golden Throne to operate without fear of tampering with the set program. To make sure it was safe, it was sent deep into space and left to drift, sheltered from the warp by a prototype Blank Engine that made it seem like an empty area of space around it. Later, one of the Blood Angel successor chapters formed by the Codex Astartes, the Eternal Sentinels, were schooled by Dorn in the maintenance and protection of the Machina, and sent to look for it, with only the last ping of its locator beacon to guide them. When they finally found it, its Blank Field, malfunctioning, caused the sensors of the flagship of the Eternal Sentinels to frenzy, causing it to crash and find the Machina on the Medieval World of George XXXV. The rest is history.