What if... an Assassin joined the Templars?

Throughout the Assassin Order's millennia-spanning history, there have been a number of singular Assassins, brave warriors and adventurers who have proved pivotal in the conflict against the Order's enduring nemesis, the Templars.

At times, fighting the Templars has been a dispassionate affair for the wielders of the hidden blades. At others, it has been as personal as a conflict can be, with the Templars responsible for the deaths of an Assassins loved ones. Even again, Assassin and Templar have been driven by romantic love for one another.

Could there not in some timeline or alternate universe, then be a reality where one of these great Assassin heroes has switched sides, standing in opposition to their usual Creed?