I thinkg that my first time posting, and since I haven't been around for a while, so I might have missed some thing. BUT
Isn't it possible they refer to Szeth, who by some reason has the lord's blade. We really don't know much about his blade, do we? And the wrong thing they did, was to arrange the whole assassination in attempt to prevent Gavilar messing up with the dangerous thing he was about to do.
Also the black light from the sphere he gave Szeth - what happens if that light is inhaled by a parshendi surgebinder? Turn him/her into a voidbringer perhaps?