If you're defeated by the Renegade Blademaster in the Warrior Blademaster duel, when he despawns in the arena he seems to drop all his gear in the arena. So when you go back, there's a set of his gear on the ground. Die again, and there's a second set. And so on, until you win.
I'd guess the intent is not to end up with a bunch of sets of free RBM gear (you do eventually have to win to leave the arena with it all in tow, so it's not quite infinitely doable and not quite free, but it seems off).
FIXED: Renegade Blademaster Duel Bug
Moderator: Aureus