Monks of the way of the Viper specialise as assassins, using poison strikes to debilitate their foes before finishing them off with precision hits to vital points.

Envenomed Stirkes

Starting when you choose this tradition at 3rd level, your unarmed attacks have to potential to inflict additional poison damage on your enemies. When you hit a creature with an unarmed attack you can expend a ki point to deal deal additional poison damage to them, that creature takes additional poison damage equal to you Venom Dice. A creature that takes damage from this must succeed on a Constitution saving throw or become poisoned.

Venom Dice: The damage your venom dice deals is 1d6, this increases to 1d8 at level 6, 1d10 at level 11 and 1d12 at level 17

Saving throw DC = 8 + your proficiency bonus + your Wisdom

Bonus Proficiency

As part of your training you have spent time perfecting poisons and antidotes. You gain proficiency with Poisoner's kit

Strike the vitals

At 6th level, you gain the ability to strike with increased precision. You can spend 2 ki points as part of your attack action on your turn to give yourself advantage on attack rolls until the start of your next turn.

Deadly Venom

By 11th level, you have learned to overcome any and all resistance to your poisonous strikes. When a creature is hit by your Envenomed Strikes you may spend 2 ki point to impose disadvantage on its constitution save, in addition if a creature has resistance or immunity to poison damage you can treat it as though it doesn't. 

Opportunist

At 17th level, you can exploit a creature’s momentary distraction when it is hit by an attack. Whenever a creature within 5 feet of you is hit by an attack made by a creature other than you, you can use your reaction to make a melee attack against that creature.