It's true that Balthazar was our enemy, and it's true that Jhophes forced out most of his spark when he turned Balthazar into a zombie. It's also true that Balthazar seemed to change - to become more human - the longer he was away from the dead magic.
He seems to have rejected the dead magic, but has the dead magic rejected him? To me, that is the bigger question. He still retains a small bit of his spark, and while he seems rather unwilling to try to grow that spark, I don't know what the Sprites have in store for him. Will they attempt to bring him back to their side, to corrupt him again? And if they do, will he come storming back with a vengeance, more powerful and more malevolent than he was before?
That thought is terrifying to me, perhaps even more because he is now our ally. It was easy to fight him when I did not know him as anything other than the Wizard of Dead Magic. But what happens if he becomes corrupted five years from now? By then, he very well may be more than just our ally; he might very well be our friend. And that would put us into a very difficult position. I only hope that never comes to pass.
Want to learn more about Jolie, Balthazar, or the Sprites? Then download Rise of the Dead Magic, Book 1 of the Three Wizards Chronicles.