The grey talon assassins are a very special group for one reason. They have never been caught. They are impossibly hard to find; many doubt their very existence. Once one has found them, they can be sure the job will be done… for the right price of course.
Carnival revelers wear masks and concealing clothes. (Wearing of masks in Venice was first documented in the late 1200s) It allows for the social classes to mix, easing social tensions.