Like the subject says, there are Curse of the Crimson Throne spoilers here. Big ones, like endgame spoilers about a major NPC/enemy.
I'm a few sessions into running a Curse of the Crimson Throne campaign for my group and I've decided to basically rewrite Ileosa to be interesting. The short version of the campaign as written is that Ileosa marries the king of Korvosa and then stumbles across the fangs of Kazavon beneath the castle, allowing Kazavon to essentially possess her. From there she becomes evil and does all kinds of awful things to the people of the city. The boring part is that the way she's written is that she already hated the city, the people, and the king, and she was already evil before the possession. It makes the entire possession element seem completely unnecessary and pointless.
My plan is to make her perhaps a bit spoiled/bratty when she arrived, but otherwise not evil. And rather than having her be 100% possessed and basically a non-character throughout the campaign, I'm going to have her be aware of what is happening and be able to break the possession occasionally (essentially like she's getting recurring Will saves and when she manages to roll a nat 20 she can act on her own free will for perhaps an hour, only to fail the next roll). I'm planning on creating something of a vigilante persona for her to use to interact with the party and try to help them save the city from the things Kazavon is making her do.
This means the endgame will change pretty significantly. I'm going to drop hints here and there and hopefully by the time the final confrontation rolls around, they'll know she's still alive in there. I want to have some sort of interesting way to allow them to break the possession that they can work towards. I looked at possession rules and those aren't really interesting enough for such a major conflict.
I'm relatively new to Pathfinder (I've played in a full AP and a handful of modules) so I'm not well-versed in the full range of magical items and spells. Any advice on cool obscure spells or items that I might be able to bring into the campaign to have the players break the possession would be appreciated. I don't need it to be strictly by-the-book as far as mechanics go, but I want something that still fits in the framework of the universe and makes sense for it to work against something so powerful.
Sorry for the long post, and thanks in advance for any input you guys have!