Where did Kayn find Rhaast?

As I was looking in Zed's lore for another theory, an idea popped up in my head. As we know, Zed and his followers took over the old temple of the ninja order. We also know that this order protected balance by fighting and capturing those who tipped the balance. We also know that Zed got special skills from a box in the temple, which had the dark secrets of the ninjas. MY THEORY: The order once captured Rhaast and kept him in the temple, which got taken by Zed and his students, one of which is Kayn. Maybe Kayn found Rhaast there and bonded with him, or he was given Rhaast as a gift from Zed, as to thank Kayn for his help in taking over the temple. What do You think?