I'll admit I haven't read the whole thing. I didn't even join until you were around chapter 18 or so... But I will say this; you really don't want people hating your protagonists. At least, not in the way that I'm coming to dislike Kail. I have no problem with cocky characters, nor ones who kill out of necessity, nor even ones who are *good* at killing and somewhat enjoy it (as long as there's a purpose, like an assassin). Him wasting people because they hurt Ellie--that's a *good* reason, in my opinion. Him kicking someone while they're down (figuratively or literally)... not so much. Of course, if he feels no remorse for what he's done... well, that shifts him a little bit into the realm of unlikable. Perhaps this has been told in one of your earlier chapters already, perhaps not... but *why* does he feel no remorse? Was he abused as a child or something? Or is he really just psychopathic?
Also, I know Kajsa is a little... ambitious in that realm, too, but would she *want* him to be a heartless bastard? Okay, he loves her, but would she be fine with him hating the whole rest of the world, so they can go off and be bitter together?
Splitting the chapter in two (to put the "beginning of the prophesy" and its resolution in separate chapters) might help, but do you really want to bore yourself and us with 20 pages of explanation on him figuring out the glow? I mean, yes, that should take more time... but I'm not sure you want a blow-by-blow account of him puzzling it through. Maybe Daddy can suspend the hearing due to janitorial work, giving Kail some time to discover a way (maybe he actually has to *do* something besides just pull it out, like, draw the glyph around the sword, or activate an ability, or *something*) to prove his worth. And it takes some time. After all, he knows very little about the glyphs besides Kajsa's little lesson (which could be some foreshadowing in and of itself). It could also allow him to come to terms with what he is--the Godslayer.
Or maybe there is a more long-standing prophecy that the trolls have to prove him "better than all the trolls in the mountain" besides Kajsa's sword. I mean, it's not really much of a prophecy when it begins and ends within a day (or 2 minutes, the way it's written now). Shouldn't there be something like one of those "There shall come a time, when a man not of this world shall rend the very mountain we live in, shake the foundation of our society to its very core, and then bind us together stronger than ever" prophecies that's oh, a millennium or so old? Especially given how long-lived trolls are to begin with. Do trolls have seers, or prophets, or anything like that? Or, another possibility would be something wrong that none of the trolls have been able to fix. Then, when Kail is able to fix it, tada. Greater than all the trolls. I understand that you want to use Kajsa's sword because it's the idea that her grandmother(?) told her about, but her grandmother could always tell her about something else instead.
I think another problem I have with the whole sword-in-the-stone issue is the trolls' perception when he pulls it out. "Well, she just keyed its release to him because she loves him," I say, sowing even more seeds of doubt in the minds of the trolls. As her father, I'd *especially* think that, given how he knows her feelings toward Kail. So how is this supposed to prove that he's greater than all the trolls? Honestly, I think it needs to *not* involve the two of them, otherwise, the perception is going to be skewed.
I really didn't have a problem with the way you ended chapter 23 and how you began chapter 25. The unreliable narrator works great in that sense. Since you're in first person, you have to show it through the eyes of the character at focus. Kajsa believes one thing, but that doesn't make it the truth. The reality is quite different, as chapter 25 shows.
Sorry for another wall of text. Hopefully you're getting something from this besides my ranting.