Okay, I have some feedback for the whole thing and I'll start at the beginning. Generally, what it keeps coming back to is I'd like to see more (in the earlier chapters).
Specifically, I have some ideas for what to elaborate on in each chapter.
In Chapter 1 Talzar has a book, but where did he get it? Again, I'd like to see this journey in my mind, maybe he went to great lengths to please his leader as a last-ditch effort to save his own life? Maybe there isn't even dialogue and we're just following and seeing his actions, Indiana-Jones-style? He crosses a rickety bridge and climbs a mountain and kills a big snake and burns some cobwebs and solves a puzzle and finally gets his hands on this guarded text with all the answers he needs, a real victory for him. Something like this would allow us to get to know Talzar a bit and doesn't spoil anything with Serpedes.
In Chapter 2 I like that Cassander's father forces him to take sword-fighting lessons, but I don't like that he just says so. Again, the chapter could easily open with him in a lesson, perhaps bored with his instructor, and after besting him with a clever trick, he makes his escape from the castle where the current story resumes. Again, it would delve into his character a bit before seeing his interactions. Alternatively, you could show a day in Talia's life prior to everything going crazy, with her waking up to the shouts of a bunch of kids in the orphanage, having to step over toys and trinkets and inventions and interact with robots and things in the house, and eventually she leaves and spots Cassander and again, the story resumes. Either way it would help establish that one of these characters is the main protagonist with whom we'll be spending the majority of our time in the story. (Hint: if you started with one of them waking up, you can use the "FirstName. FirstName! Good morning, FirstName." template set by the two games for a nice thematic tie-in.)
Some parts of the conversation felt rather expository and gave away too much information that the characters wouldn't really talk about. Most of it was rather natural, though, and the two are believable friends and somewhat interesting characters. If I were you, though, I'd add some kind of unfulfilled love element between the two and/or some kind of personality quirks for each that can be seen as a negative trait, to keep them from being "perfect little mary sue" type of characters. Maybe Talia is embarrassed by her mother and feels inadequate mentally because she can't match up to Lucca's genius, and maybe Cassander has horrible stage freight and prefers to go unnoticed, and as such he feels unworthy of being the future king. I mean, they both have a lot to live up to, and their lives, though at peace, probably aren't always easy. That should be acknowledged somehow in a way that can be overcome in a character arc.
In Chapter 3 mere soldiers overwhelm the legacy characters, as previously mentioned. However, in Chapter 1 Serpedes' soldiers seemed to be ghosts or lost souls or something like that, perhaps their ghastly qualities could be emphasized more? Perhaps you could describe them materializing like a solid coming from air and skipping the liquid phase. If they are undead that brings a relatively useful "unkillable" enemy to the playing field that could believably take on said heroes, but make sure to give them a weakness or you have enemies that you have to deal with in the story later that are still unkillable.
Also, Lucca seems to have a lot of precognitive knowledge of her own imminent doom and that's not really explained. I'd like to know what gave her the idea that "it's all happening again" etc.
In Chapter 4 I still don't get why Kid can just waltz in, or why she's really there(from a storytelling perspective). I don't mind her being there but why didn't Talia mention her earlier? Why not use Talia instead? Where is Talia? The question is asked, so the answer had better be good when we find out, for the sake of the story. I don't mind what's actually happening, I just have questions that could be answered here.
Chapter 5 is pretty awesome, I like that Serge and Kid are together, it's a well done flashback and fills some holes nicely. I also like that the narrative splits and gets creative, and finally, I am enjoying the new, longer length with the most recent addition.
These are mostly just ideas and questions to help you, though I admit I may have rambled a bit and gotten commenty, as I was re-reading while typing to make sure I was all caught up. Hope some of it helps! Keep writing.
One last thing, you could always set up a Google Doc version, where it's all in one document and you just post the link and let others view but not edit it. That way you could format it however you wanted rather easily without the problems of ff.net and even include a table of contents as the first page that linked to the chapters, or whatever you want to do with it. Just a suggestion for a free alternative method of storing and sharing stuff without having to actually download anything new.
