The Temple of Atropos was a temple on the planet Time. It contained the Mouri as well as the Priest Triangles. (TV: War of the Sontarans)
History
The Dark Times
According to Swarm the Temple of Atropos on the planet Time was set up by the Division to end the Dark Times by having Time surrender to Space through the Mouri.
Siege of Atropos
The Fugitive Doctor was sent on a mission by the Division to enter the Temple as part of the Siege of Atropos, which had been taken over by Swarm and Azure, and reinstate the Mouri. Her, Karvanista, and two other Divison agents achieved this by hiding the Mouri inside a Passenger, tricking Swarm and Azure into releasing them back to where they belonged.
The Thirteenth Doctor, whilst inside her time stream, witnessed the Siege of Atropos, with herself, Dan, Yaz, and Vinder taking the places of the Fugitive Doctor and her companions due to the time storm affecting their time streams. (TV: Once, Upon Time)
The Mouri were subsequently quantum locked against Swarm and Azure to protect them. (TV: War of the Sontarans)
The Flux
The inner sanctum of the temple was damaged by the Flux, leaving two Mouri broken. Vinder and Yasmin Khan found themselves in the temple and Priest Triangles demanded to know if they could repair. Swarm and Azure returned to the temple and killed two more Mouri, subsituting Yaz and Vinder in their places. They lured the Thirteenth Doctor, along with Dan Lewis, to the temple and revealed what they'd done, with Swarm preparing to expose Yaz and Vinder to the full force of time. (TV: War of the Sontarans) The Doctor chose to put herself and Dan in the other broken Mouri's places and sought to control the ensuing time storm, managing to have the surviving Mouri hide four Mouri within the Passenger that Swarm and Azure had brought to the temple. The Mouri did so, repairing the temple and freeing the Doctor and her companions, however Swarm revealed that time had been broken long enough to release particles of the Time Force. He and Azure departed, with the Doctor and her friends also leaving the temple. (TV: Once, Upon Time)