In a way I'm starting to wonder how much all the specifics of the tangled stuff matter. I mean, it's theoretically possible that for some reason the whole "Forbidden Spell" and killing everybody and all that was in the service of some good so great that if I knew I'd be all "Well, it sucks, but those puppetmasters had no choice".
But in practice, no. Puppetmasters with means that involve mass slaughter and betrayal never have very good ends behind it. Sometimes they theoretically do, if you were to ask them they'd have a justification that sounds noble, but if you look at the results of both particular vile deeds and the process in general you start to realize that it actually either doesn't advance those supposed goals at all, or at best does so far less well than non-vile approaches would. Usually underneath any justifications the real motive is "more power for me and mine".
So my point is, there's a puppet master out there and he's trying to get people to help him do stuff and he's occasionally trying to kill people and so on. Maybe it's Lucas; he's surely at least involved. Whatever he's specifically after, it's almost certainly bad, so the real urgency is to identify who's working for him, turn them, and find the bad guy. At that point if you want to know the truth, you could try beating it out of him, but it might be safer to just get rid of him . . . ideally not by magic.