Who is Fedmahn Kassad from The Rise of Endymion and what is their importance?

Fedmahn Kassad was one of the original Hyperion pilgrim. Because of his relationship with Rachel, he has become a man out of time. He is described as a fierce warrior and military tactician. Eventually, we will see this character travel into the distance future where he will become the template used to create the assassin, Shrike.