Roguish Archetype - Iaijutsu Master
Iaijutsu is the technique of drawing your weapon - most commonly a katana - and striking with it in one fluid motion, often doing so to catch your opponent's off guard with a particularly vicious strike. Some rogues have adopted this exotic technique as a way to exploit opponents and ensure that their sneak attacks are deadly effective.
The iaijutsu master learns a variety of techniques not dissimilar to those of a monk, and the two are closely intertwined. At higher levels they even gain mystical abilities, allowing them to declare duels against opponents to engage them in single combat. With blinding speed and devastating power, the iaijutsu master is a foe to be feared on the battlefield.
Iaijutsu
At third level when you take up this archetype you master the use of the katana (longsword) as a weapon of the rogue. While wielding a katana in one hand and having nothing in your other hand, you may attack with it as a finesse weapon that qualifies for sneak attack damage.
In addition, if you draw your weapon before making an attack you don't need advantage on the attack roll to use your Sneak Attack against a creature if you are within 5 feet of it, there are no other friendly creatures within 5' of it, and you don't have disadvantage on the attack roll. All the other rules for Sneak Attack still apply to you.
Ki
At 3rd level you gain ki points equal to your rogue level. These can be used on a number of features.
Lightning Blade: When an attack is made against you by a creature within 5', you can spend 1 ki point as a reaction to sheathe and then quickdraw your weapon to attack first, with advantage, potentially interrupting the attack before it occurs.
Second Strike: You can spend 1 ki point as a bonus action to attack a second time with a melee weapon during your turn.
Swift Action: You can spend 1 ki point to add your proficiency bonus to your initiative rolls. This lasts until the end of your next short or long rest.
Guiding Winds: You can spend 1 ki point to find the shortest, most direct physical route to a specific fixed location that you are familiar with on the same plane of existence, for 1 hour. Alternatively, you can use this to locate one creature or object (either specific or generic) within 1000 feet.
If you multiclass with monk, your ki points stack with those you gain from monk levels, assuming you have reached 3rd level in the monk class. Any ki expended is regained upon completion of a short or long rest.
Cunning Sheath
From 9th level whenever you use your Cunning Action or Steady Aim, you can choose to sheath your weapon at the end of your turn even if you have used your normal Object Interaction that turn.
Ki Advancement
You gain four new uses for Ki at 9th level in this class:
Explosive Strike: You can spend 3 ki points when you make a successful sneak attack to increase the number of dice rolled by half (rounded down).
Canny Defense: You can spend 1 ki to add your intelligence modifier (minimum 1) to your armour class. This lasts until the end of your next short or long rest.
Merciful Recovery: When you take damage you can spend 1 ki point at no action cost to expend a number of hit dice up to your proficiency bonus, regaining hit points as if you had spent them during a short or long rest.
Third Eye: As a bonus action can spend 4 ki points to gain Truesight out to 60' for 1 hour.
Declare Duel
From 13th level as a bonus action on your turn you can declare a duel with another creature within 30'. When you do so, the target may choose to refuse or accept. If they refuse, all attacks you make against the target for the next minute have advantage due to their cowardice. If they accept, both you and your target are transported to a temporary demiplane alone. The demiplane takes on whatever appearance you wish, though it must be well lit and have no environmental features that can impact on the duel.
While in this demiplane you and your target can only damage or affect each other, and likewise you and your target are immune to any effects or damage from those not in the duel.
The duel lasts for 1 minute or until one participant dies. During the duel any of your sneak attack damage rolls that are either a 1 or a 2 are treated as a 3. Upon conclusion of the duel both participants (living or dead) are returned from the demiplane. If there was a victor, they instantly regain half of any hit points lost during the duel.
Declare Duel can be used once, refreshing on a short rest. If it has already been expended, you can use it again by spending 3 ki points.
Strike from the Void
At 18th level you can choose to expend all your movement on your turn to teleport up to 60'. If you then attack, you do so with advantage and add your Intelligence modifier to the damage roll.
In addition, you no longer provoke opportunity attacks while moving normally.