I caught up with my other editing projects and started to take a look at Tykis' Document. I went through the Purifying scenes and just stopped at the Corruption part. I made some notes (just opinions, suggestions, humorous observations). They are just one person's thoughts, others can disagree. I understand it can be be hard to take over an existing character (assuming you want to keep their written and established personality close).
If I had a comment that differed from the writing, I would say that I wouldn't treat him as having a libido problem, though I get it. Sex with corrupted creatures is well-known in game to cause such things, and I am not saying he doesn't have that going on. But I think there's a more unique and special 'curse/problem' that he could have. He almost universally and consistently mentions that it's not his arousal or horniness or lust or hard cock that bothers him, it's that he can't ejaculate or cum on his own (at least not with great difficulty). Naturally, he will be in a state of arousal whenever the Champ meets him and he needs help, so understandably it might be misunderstood that his issue is just getting hard a lot, when it seems like the issue is that he gets aroused... and can't reach climax (which I think most of us might agree is way more frustrating).
Why would Kasyrra do this? She's a demon, I know there's a scene where you mention him to her (for the Corruption path). I certainly wouldn't expect you to rewrite it, but if you wished to explore a more unique path (making it clear that Kasyrra can and does things that ordinary demons can't, such as literally change peoples' bodies or aspects, as opposed to just their own or through tainted sex). You could have her mention how he was so thrilled, Tykis said he'd never climaxed like that with anyone but her... and so she left a little magic that made it so that she was the only one that could bring him to climax (and she did for a little while, before moving on to the Alraune or the Hornet hive or wherever she went at that time). Of course, being a demon she doesn't concern herself with his troubles currently.
And then when the Champ mentions that he manages to get the elf boy to cum, she can look amazed or curious or startled and remark that maybe a bit more of her essence rubbed off on the Champ from the portal explosion than she realized and maybe that's why he's able to bring Tykis to orgasm. And she says that's why he'd be perfect for helping the elf boy deal with his problem (obviously in the Corruption way). I think this plot would emphasize Kasyrra's impact on the world and the Champ's link to her, as well as his own impact on the world and ability to enhance or resist Kasyrra's influence. That's only my opinion, of course, and I wouldn't expect you to want to have to tweak a lot of writing you made. I certainly would help if you did, but I am not going to make those suggestions in the Doc otherwise. I just wanted to share a thought or observation I had on the elf boy from the current lore and scenes.
Other than that, I hope the suggestions are helpful or at least amusing. I will go through the remainder later tonight after work.