Ronin Rogue

Most rogues are opportunistic scoundrels, often enough outright criminals; but not all originally come from honour, from duty, from a disciplined study of the blade under a master. These rogues, often called Ronin, have abandoned their previous life without a choice, whether through exile or by their master dying. They now roam the land, trying to find a new purpose as wandering travellers.

In battle, they wield special blades called katanas, wear heavier armor than expected from rogues, and they move with practiced swift perfection, slashing across their enemies with technique and devastating damage. 

Instruments of the Wanderer

Beginning when you pick this archetype at 3rd level, you gain the ability to use the tools of a wandering ronin. You gain proficiency in medium armor, in the longsword if you don’t have it already, and in one set of artisan’s tools of your choice.

In addition, you’ve learnt to use a special type of longsword known as a katana, which when wielded by you, has the finesse property.

Ronin Slash

Also at 3rd level, you can use your katana to devastating effect. Whenever you deal Sneak Attack damage with your katana,  you can choose to delay part of the strike for greater impact. If you do, you deal half your Sneak Attack dice of damage with the attack (rounded up). 

At the beginning of the hit creature’s next turn however, they take the remaining half of the Sneak Attack + half your Rogue level (rounded down) in damage. You gain temporary hit points equal to half the damage dealt this way. 

Sweeping Blade

Starting at 9th level, as an action, as long as you’re wielding your katana, you can execute a devastating attack. You move forwards, up to 30 feet in a straight line, without provoking opportunity attacks. You can move through other creatures this way, and if you do, they must succeed on a Dexterity saving throw (DC= 8 + your proficiency bonus + your Dexterity modifier). On a failed save, creatures take slashing damage equal 1d10 + your Sneak Attack damage dice + your Dexterity modifier, taking half as much damage on a successful save. Once you use this feature, you can't use it again until you finish a short or long rest. 

Furthermore, you can move through other creatures without suffering any penalty to your speed.

Master of the Blade

At 13th level, you gain the following features. 

Masterless. You gain a d4 bonus to any saving throw or check you make against being charmed or mind controlled in any way.

Flawless Technique. As long as you have temporary hit points granted by your Ronin Slash feature, you can use your Sneak Attack against the last creature that took damage from the feature even if you don’t have advantage on the attack.

Tenacity. Whenever you reduce a creature to 0 hit points, you gain temporary hit points equal to half your rogue level. If a creature was reduced to 0 through damage dealt by your Ronin Slash feature, the temporary hit points granted by the feature are doubled instead.

Steel Tempest

By the time you’ve reached 17th level, you have managed to become a relentless storm of blood and steel on the battlefield. 

If a creature fails their saving throw against your Sweeping Blade feature by 6 or more, you reduce a creature to 0 hit points while wielding a katana or score a critical hit with a katana, you can immediately use your Sweeping Blade feature (no action required) without expending a use. You can only do so once per turn.