The Thief is not charming. He does not play fair. He does not follow the laws of war. He is not chivalrous. He is a Thief. He is a bastard. And he will do whatever it takes to win. He’ll blind you with dust and stab you in the gut. He’ll knock you over the head with a blackjack and then pound your face into the floor. He’ll use gadgets to get the upper hand. He will cheat.
Because he is no rogue. He is a Thief. Simple as that.
The full class can be found here at Chronicles of the 13th Age