Mouri

The Mouri were a group of six entities kept in a state of stasis in the inner temple of the Temple of Atropos, standing on each end of a hexagonal platform. They wore white garments and had vertical inscriptions on their faces. Although the original six Mouri all appeared to be female, this did not seem to be a requirement for the function.

The Mouri were "assigned" at the beginning of everything as a means of keeping control of Time. The Priest Triangles, which were assigned to serve and guard the Mouri, believed that this was done because Time in its more natural form was "destruction" or even that Time itself was "evil". When the Temple was functional, all time would pass through the Mouri, who would keep it under control. The process could destroy lesser beings such as humans in second, with the Mouri being "especially equipped" to withstand the process.

Swarm and Azure once attempted to harm the Mouri, leading to them being imprisoned by the Division. Additional precautions were taken to protect the Mouri, who were quantum-locked: they would only become visible if a living being stepped onto the platform, and Azure and Swarm would not "count" for this purpose.

However, the Flux damaged the Temple gravely, harming two of the Mouri, which began to flicker between their normal appearance and a charred, faceless one. Shortly thereafter, Swarm and Azure returned to the Temple alongside Passenger. After destroying two additional Mouri completely, Swarm inscribed the requisite symbols on the faces of Yasmin Khan and Inston-Vee Vinder and made them replace the two Mouri as a "short-term repair"; as he prepared to let the full force of Time begin to blast through them, Swarm taunted the Thirteenth Doctor with the knowledge that they would die within moments. (TV: War of the Sontarans)

Behind the scenes
The Mouri's name is a corruption of the, the Fates of Ancient Greek mythology.