Eternal Supplicant
Mirror universe
The Eternal Supplicant was the title given to the life-long slave to the Terran emperor.
In the 23rd century the title was bestowed on the runner-up in the Terran contest for the throne. Once two contestants remained alive from a trial of slaughter, whoever was able to murder their family first would be crowned emperor. The other, either due to weakness or hesitation, had their life given to the new emperor only to serve at their heel. San served Emperor Philippa Georgiou in this capacity when he failed to kill his family before she did. (Star Trek: Section 31)