The Northern Fortress is a fortress owned by the Nohrian royal family. It is located northeast of the Nohrian capital of Windmire. After the Avatar was kidnapped from their Hoshidan family, Garon sent them to be raised there. Since he viewed the Avatar as weak, he refused to let them leave the fortress until they could prove that they were battle worthy to him.
The Avatar was not always alone; their Nohrian siblings, Xander, Camilla, Leo and Elise often visited them during their spare time. Xander usually came to use the fortress as a combat lesson for the Avatar so that they could return to Windmire. During the Avatar's stay, they also with their four retainers ; Gunter, a veteran soldier who personally trained them, and their servants Flora, Felicia, Jakob and Lilith.
Early on in the start of Fates, the Nohrian royal siblings visited the fortress. Xander tested the Avatar in combat, and after being defeated, told Garon that they were ready to fight. Garon, pleased with this outcome, allowed the Avatar to leave the fortress after staying there for so many years.