I am talking about the kind we see in fiction like the faceless men in game of thrones or the Assassins from the Assassins creed video games. Also what happened to them? Are they still around killing people today?
There was an Islamic Order of Assassins, also known as the Nizari Ismailis. I think they are where the term assassin comes from. They killed many Islamic leaders but were destroyed in the Mongolian conquest of Khwarezmia after the assassins failed to kill a Mongol general.