Peacekeeper

Sanctioned assassins who silence threats by any means, be it cunning sabotage or through eruptions of elegant slaughter. They ritually conceal their faces, bound by unbreakable oaths and famous for their elegant sword dances using shortswords and daggers. Those who underestimate them often find a crossbow bolt or dagger sprouting from a chink in useless armor, the lesson learned too late.

Skilled Swordsman

You choose to join the order of Peacekeepers. They teach you the way of the Sword and Dagger. When you are wielding a melee weapon in your dominate hand and a dagger in your non dominate hand, you gain a +2 bonus to Damage Rolls with both weapons.

Follow Up Strike

The Peacekeepers teach you to strike quick. After two hits to an enemy you find another opening and can strike a creature quickly with your dagger. If you hit on your first strike and hit a second strike with a dagger you can follow the strike up with another dagger strike. If the follow up strike hits you can make another follow up strike up to 3 total Follow Up Strikes. Your attack modifier is not applied to the Follow Up Strikes. 

Poisoned Strike

At the 9th level you have learned how to coat you dagger in poison. Your follow up strikes now deal Poison damage. A creature subjected to this poison must succeed on a DC 11 Constitution saving throw, taking 3 (1d6) poison damage on a failed save, or half as much damage on a successful one.

Keeper of the Peace

At the 13th level you have mastered keeping peace. You are now able to arrest hostile creatures. As an action you can attempt to subdue any foe who you can communicate with in combat. They must make a charisma saving throw (DC 8 + Your Intimidation). On fail they will no longer try to fight you. If you or the foe are hit this effect wears off and they may become hostile again.  

Peace of Shadows

When you reach 17th level, you are a master Peacekeeper. If you are hidden from a creature you may make a melee attack against it with +1 bonus to hit. If the attack hits, the creature must make a Constitution saving throw or fall unconscious. This action doesn't generate any significant amount of audio or visual disturbance. For a creature to notice, it must make a Perception check with a DC equal to your rogue level + your Dex modifier + 8.