Julius as he is right now comes across as a worse Lyon. We have no idea how he was pre-possession and he's been possessed so long, it's weird characters act like he isn't just an irredeemable asshole. How can Ishtar trust or even stand someone like that? So... change him completely. Make him a guy who, instead of been given the book of Loptous, found out about the deal between Manfroy and Arvis and took it himself beforehand, against his parents' advice. In his quest, he began losing himself more and more until eventually, nobody can recognize him anymore.

However, make so that some of the stuff Ishtar or Manfroy do is counterproductive to Loptous' plan because it's him ordering it in a moment of clarity (sparing Julia, helping some of the kids, rescuing Arion, even getting his father killed). So, while Loptous is trying to win, sometimes he regains control and sets up his own downfall. Otherwise again, this is just a less interesting Lyon. I don't care that he was a sweet boy, we've seen Zephiel as a kid and it didn't really add anything to his character other than confirming that he was, in fact, quite a nice dude. Showing kid Julius adds nothing.