The Sevenfold Sanctuary is a location in Fire Emblem Fates.
The Sevenfold Sanctuary is a seemingly abandoned place high atop the mountains of Notre Sagesse. It is rumored that the Rainbow Sage lived up there and would grant great power to those who passed his test. Many ventured up to claim this power, but few survived to tell the tale.
The Sevenfold Sanctuary is first visited in Chapter 19 where the Avatar and their Hoshidan allies enter to speak with the Rainbow Sage to gain power for the war effort against Nohr. When they reach Notre Sagesse through Leo's warp tome, the Avatar flags down an old man who directs them to the sanctuary. After climbing up a steep mountain, they reach the sanctuary and prepare to take the Sage's test.
After stiff resistance from the shades residing in the sanctuary, they encounter a door in the final room. The Avatar opens the door, and the whole group is transported back to Notre Sagesse. The old man laughs at the Avatar, who realizes that he is the Rainbow Sage. They ask him if he could grant them power, and he tells them that their newfound power came from defeating the shades. He enhances the Avatar's Yato into the Noble Yato.
The Sevenfold Sanctuary is visited in Chapter 11. Under Garon's orders, the Avatar captures Notre Sagesse and decides to find the Rainbow Sage. They find him in the Sevenfold Sanctuary, where he is held hostage by the Hoshidans to prevent him from granting untold power to Nohrian forces. Despite the attempts of the Hoshidan army led by Hinoka, the Hoshidans are eventually routed out of the sanctuary. The Rainbow Sage gave the Avatar's Yato a little of his power, before Iago tells the Avatar to kill him. The Avatar is unwilling to do so, but Iago points out that they cannot let the Hoshidans claim the power too. The Rainbow Sage decides to take his own life instead, as he had already done his part and had expressed a desire to die for a very long time, much to the Avatar's disappointment.
Like in Birthright and Conquest, the Sevenfold Sanctuary is visited in Chapter 15, where the Avatar, still unsure of what Izana meant by "find the dragon", decides to seek help from the Rainbow Sage. Under his disguise as an old man, the Rainbow Sage redirects them to the Sanctuary to face his trials. After defeating the shades infesting the sanctuary, the Rainbow Sage congratulates them for passing his trials and enhances the Avatar's Yato into the Alpha Yato.