The Banner of the Kage was a Templar Tradition from back at the orders original inception. It was the brain child of Tera Byssta much like the Templars of Twilight Insignia. She believed, and it was accepted that, being Kage was a symbol of importance to the individual, and to the Templars as a whole. Each Kage was different, and as such each age of the Templars was different during the reign of that Templar. So at her suggestion, and the agreement of the council, every Kage upon being selected had a banner designed for him, that would be unique.