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, who were assigned to serve and guard the Mouri, believed that this was done because Time in its more natural form was "destruction", even "evil".

When the Temple of Atropos was operational, all time would pass through the Mouri, who would keep it under control. Being in their place could destroy lesser beings such as humans in seconds, but the Mouri were "especially equipped" to withstand the power of time.

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. Azure and Swarm were specifically excluded, as known enemies.

In time, the Flux gravely damaged the Temple, harming two of the Mouri, who began to flicker between their normal appearance and charred, faceless ones. Shortly afterwards, having freed themselves at last, Swarm and Azure returned to the Temple alongside Passenger. Swarm atomised two of the Mouri, and inscribed the requisite symbols on the faces of Yasmin Khan and Inston-Vee Vinder, who were to take their place.

Swarm described Yaz and Vinder as "short-term repair". In the Thirteenth Doctor's presence, Swarm prepared to let the full force of Time begin to blast through them, taunting the Doctor with the claim that they would surely die in moments. (TV: War of the Sontarans)

Behind the scenes
The Mouri's name is a corruption of the, the three Fates of Ancient Greek mythology, one of whom was herself named.