David Walters. You get to play out Avenger's early life and find out how he/she came to be orphaned on the steps of a monastery dedicated to forgiveness, gnomic epigrams, and garotting.
Fabled Lands Publishing only owns the rights to the original six books) so if you want a copy you'll need to hie your way over to Megara Entertainment and see if they have any spare after supplying the Kickstarter backers. In fact, I just this minute got an email from Mikaël Louys, who runs Megara, to say that he has a few copies of Ninja for sale. Better be quick!