I had a lot less to do with the writing of the fifth book than the rest of the series. Oliver Johnson was supposed to write it, but ran out of time. Luckily Jamie Thomson was on hand to step in, but necessarily it was a rush job so he didn't have time to read the earlier Blood Sword books. I came in right at the end to tie up the last 40 sections or so.
Patreon backers can see how I'd have liked the series finale to pan out. Tambù's Blood Sword 5e campaign and rulebook drew on those notes, and I have a feeling so will Prime Games' forthcoming CRPG.
Various player-characters guest starred in the Blood Sword books, in a manner of speaking. This time it was the turn of Zaraqeb (Zara in the book) and Karunaz, who were played in my and Steve Foster's Empire of the Petal Throne campaign by Gail Baker and Paul Mason. The original PCs weren't a lot like their gamebook incarnations, incidentally. The real Zaraqeb wasn't a sorceress and wasn't that nasty; the real Karunaz was neither posh nor noble, though he was a much more interesting kind of hero because of that.