WARNING: SPOILERS!! This is based off of Chapter 36 of the book "The Last Life of Prince Alastor" by Alexandra Bracken. What's happening: Alastor is about 99% dead and about to be dead completely, after giving up his energy to save Pyra. Prosper was able to speak to Alastor with his thoughts, so he begged him to return. Alastor would not listen. Prosper used his true name, Stingingbow, to compel him to hold on to a small bit of his power, just enough to stay alive.
Thanks so much to @TheBroCodes for the animation and Alastor/Stingingbow's (the fox) voice!! Prosper was voiced by me.