Cloud Ruler Temple was the original stronghold of the Imperial Blades. It stood on a mountaintop in the Jerall Mountains in the very northernmost reaches of Cyrodiil, above the Nord city Bruma by the very border of Skyrim itself. It was a fairly simple walled monastery, difficult to reach and all but impregnable. Its destruction by the Thalmor during the Great War also resulted in the destruction of many records of the Blades and their famous ancient quarry, dragons.
It was here at Cloud Ruler Temple where Martin Septim was assisted by the Blades in taking the throne of the Empire and discovering what was truly needed of him to stop the Oblivion Crisis.