Avatar: The Last Airbender: Legend

Avatar: The Legend of Aang.
Torn by internal strife, the Earth Kingdom has been at war with the Fire Nation for sixty years.
In a small village near the conquered city of Lu-Yang in the northwest of the continent, a son, Guan Yu, is born to an officer in the Fire Nation's army.

The events will take place 40 years before canon. There will be many new characters and new cities. I searched but couldn't find the names of most of the rivers, seas, forests and mountains, so I'll be naming them myself.

patreon.com/FanFictionPremium