Shadows of self (Mistborn Book 5), Brandon Sanderson

Join the hunt for a mysterious assassin The criminal elite of Elendel were invited to an auction - which became a massacre, when an unknown assailant slaughtered everyone in attendance. Now Wax and Wayne, both able to use magic, both lawmen from the rough and ungoverned frontier territories, are on the case. All the clues suggest the killer is a rogue kandra - a secretive, almost mythical, figure who acts from the shadows - called Bleeder . . . and that the governor is her next target.

Bleeder, and the conspiracy behind the killings, has to be stopped . . .

before the city is plunged into chaos.