Hi Gee! Sorry for how long this has gone on, we can definitely bend the plot to be easier to work with, especially given how wonky things have been. This was the first thing that came to mind, let me know if this works or if you would rather amend it further. This can be back-dated or handwaved.

As the cult is not terribly likely to welcome him back after so long in captivity, and having been interrogated by Nox in ways he's certain his poor mage soul won't easily forget, Montgomery himself is becoming a little more desperate to please his captors. He's attempting to aid them as best he can, but the contract in place is troublesome.

So he suggests a rewrite of his reality.

Rewrite may not be the best word. A little massaging, really. Montgomery, after so long in captivity and knowing that he has no escape, will become more desperate to tell them what he knows. He can't tell them as Montgomery, but if they were to, say, use their mighty meta powers to make him someone else then he would be able to speak to them freely.

And the spell for that lies within the book of Arcane magic, located within the very heart of Sunset Falls' forbidden section. It's heavily guarded and warded, and will take the best of the best spellcasters, reality warpers, and at least one particularly skillful acrobat to get into. With that book in hand, they could carve a new future for this young man.

And if they do, he'll be happy to tell them everything he knows.