Shadow of the Immortal

The ruler covets the Xanthus Elder's life-extending medical skills and sends spies to infiltrate the Xanthus world and poison the Elder. The Xanthus Elder, poisoned and attacked by assassins, encounters Sam Jenkins, who looks just like him. After dealing with the assassins, the Xanthus Elder transfers his skills to Sam Jenkins, appointing him as the new Xanthus Elder temporarily, and tasks him with finding the mastermind behind the assassination.