I know that many people belive that Janner comes back to life after TWatWK and have good reasons to.
But I disagree.
I belive that the sacrifice for un-transforming the Fangs and the Cloven is somebodys death and therefore Janner dies and stays dead.
And many say that the story whould be to sad if Janner stays dead but I also disagree with that, too.
Janner is now safe, with the Maker and his father, Esben.
So, really, the ending isn't all that sad at all.
I'm quite satisfied with it.

I believe that Janner lives. My reasoning:
Janner's sacrifice kinda represented Jesus' sacrifice, therefore coming back to life is very much part of it.
If they did find the Well, Janner would come back.
They did find the Well. Artham can't keep his wings, and if he does, he still needs healing.
SARA! Who else would she go to? Sara will need someone to care for her when she's an adult, and honestly, I can't see her marrying anyone else. (Don't say Kal, because he marries Galya)
Nia. Kal can't take care of her. Nia needs her 13-year-old son to take care of her now that Esben, Podo, and Rudric died.
Kalmar. Who else is going to be his Throne Warden? And he needs a LOT of help to run the kingdom, he can't do it by himself, and Artham can't just help him along. Artham doesn't have the total instinct to protect Kalmar, because he did not grow up with 'protect Kalmar' drilled into his head. Artham grew up with 'protect Esben'. Kalmar needs a Throne Warden who grew up with 'protect Kalmar' drilled into his head.
And as Rosalina said, IN THE PRINCE OF YORSHA DOON, Oskar said that Anniera had been returned to its former glory. Anniera wouldn't have been returned to its former glory without Janner. I will not change my mind.😑
Leeli. She can't stand High King Annoying with out the brother who doesn't mess with her.
And then there are other reasons.
At the end of TWatWK, there is a picture of the Well, therefore they must have found the Well.
Nugget. In the show, Nugget was not breathing after the battle. So Peet had take the dog to the treehouse, which probably took hours, and then he had to find the Well water, with the fact that the kids he was trying to protect were in danger. That dog was dead by the time Peet gave him the Well Water. Therefore, Nugget was resurrected. If he was resurrected, then that means if they gave Janner the Well Water, then Janner would also be resurrected. 🙃