Void dragons serve an important purpose in their own pocket of reality, namely, keeping the fabric of time in check. And this very purpose is what has brought these sentinels of time here. Tracking Kairos all the way to the Vale to have him right the wrongs he has done to their cherished timeline. Expecting a fight, the void dragons were pleased to find him in a more than cooperative state. Kairos was already waiting for their arrival and was preparing to help them, he is the Dragon of Time, after all. Some void dragons have remained in the vale since then, serving their new purpose as envoys from the Void. Envoids.
