How would you do this?

[Spacehamster]

If you wanted to homebrew the kensai from 2e into 5e, basically a fighter subclass that focuses on just 1 melee weapon and becomes a master with it and wears no armor fighting? Were thinking he would do more damage then other fighter subs but all his abilities only work while not wearing armor. Question is what type of armor calculation? Not as good as monk or barbarian were my thought so probably 13 + DEX?

What type of sub class features would you give him? Were thinking WIS to damage with his chosen weapon prob at 10 or 15 at least.

[Shining Wrath]

Start with Barbarian.
Allow him or her Expertise in exactly one weapon, chosen at level 3 when the archetype is chosen. As proficiency increases with level this bonus increases.

At levels 6, 10, 14 allow some minor benefit, maybe +1 to AC.

[Spacehamster]

Start with Barbarian.
Allow him or her Expertise in exactly one weapon, chosen at level 3 when the archetype is chosen. As proficiency increases with level this bonus increases.

At levels 6, 10, 14 allow some minor benefit, maybe +1 to AC.

Hmmm barb could actually work, his rage would be more of a combat trance, and yep one melee weapon + proficiency with thrown weapons. At 3 when you get the sub you get to dual wielder style and a slight bonus while wielding the weapon of choice.

Well would still have prof with all weapons just not getting his weapon specific bonuses when using another weapon

[Shining Wrath]

I've always thought that "rage" was an awkward choice for the barbarian's battle focus. Some guys do go berserk, but some go into a focused fugue, and some just get intense.

[Spacehamster]

As to pulling off the kensai with MC I would probably start with 6 levels shadow monk followed by 2 warlock and remaining 12 in Champion, mobile unarmored fighter that hits hard. In the end would get 22 AC unarmored with dual wielder feat + mariner style and moves with unnatural speed(teleport and monk movement bonuses).

Or 12 champion, 2 monk and whatever 6 levels of a class that compensates for loosing 1 attack from fighter 20.

[Biggstick]

As to pulling off the kensai with MC I would probably start with 6 levels shadow monk followed by 2 warlock and remaining 12 in Champion, mobile unarmored fighter that hits hard. In the end would get 22 AC unarmored with dual wielder feat + mariner style and moves with unnatural speed(teleport and monk movement bonuses).

Or 12 champion, 2 monk and whatever 6 levels of a class that compensates for loosing 1 attack from fighter 20.

I mean, what's wrong with just going Shadow Monk 18 / Warlock 2? The 2 levels of Warlock for just a touch of magic and then the rest of Monk goodness? You could even go one more level of Warlock if you want to get Darkness or other sweet level 2 spells on a short rest return. You'd also be picking up a sweet pact bonus, and any route gone here would be great flavor for a primary Monk.

[Hrugner]

I agree, Barbarian base is probably better.
3: Kensai can treat chosen weapon as if it had the finesse property. Kensai can use the attack action to make a single attack that automatically crits and ends his rage, you can not use your bonus action to rage again till your next turn.
6: Kensai can treat chosen weapon as light(but not one handed unless already one handed). Kensai gains proficiency with smithing tools. Kensai can trance as an elf rather than sleep.
10: Kensai can treat chosen weapon as a 10 foot reach weapon(20 if whip). Kensai can treat chosen weapon as if it were any simple weapon retaining only its damage dice and weight.
14: The Kensai treats every square he has occupied on his turn as if he threatens it for the round. The Kensai's reaction is only spent when used on targets higher in the initiative order than himself.

Something like that?

[Kane0]

Submortimer created an excellent Kensai subclass for the fighter, perhaps have a look at that?

[Spacehamster]

I mean, what's wrong with just going Shadow Monk 18 / Warlock 2? The 2 levels of Warlock for just a touch of magic and then the rest of Monk goodness? You could even go one more level of Warlock if you want to get Darkness or other sweet level 2 spells on a short rest return. You'd also be picking up a sweet pact bonus, and any route gone here would be great flavor for a primary Monk.

Mostly cause just monk on its own does not feel Kensai at all need more martial then monk. :)

[vincegetorix]

Many sites did the Kensai as a monk's archetype for an Unarmored/arrow catching PC. If you look at the kit from 2nd edition the kensai gets:
- An AC bonus (-2), but cant wear armor
- Bonus to hit with one specific weapon
- Bonus to damage with one specific weapon
- Training in etiquette and and art related stuff
- Bonus to initiative
- Maximized damage 1 turn/day

I'd say those thing arent to hard to change into a fighter archetype.

3: Chose your Chosen Weapon. The Kensai knows how to deflect an incoming blow with his weapon and his natural grace. Add you Proficiency Bonus to your AC while unarmored and wielding his chosen weapon (starts low but become higher than a monk's unarmored defense).

7: You can fell one enemy in one quick blow. You gain advantage on Initiative rolls while wielding your Chosen Weapon. During the first round of combat, you get a 10 yards bonus to speed.

10: Gain training in Performance and Calligrapher's tool.

15: You add half your profiency bonus to the damage dealt with your chosen weapon.

18: Kai: Once per day, you can maximize the damage dealt by your chosen weapon for your entire turn. Attack rolls against you have advantage until the end your next turn.

[Falcon X]

Middle Finger of Vecna did a pretty strong Kensai that you can borrow from: http://www.middlefingerofvecna.com/2015/05/kensai.html

[LordFluffy]

I think even without hombrew, you could do a Monk 1/Fighter: BattlemasterX/Maybe with a level or two of rogue for expertise and mobility options.

If I were homebrewing, I'd still take the monk as the base. Maybe making it so you can spend ki to double your prof bonus for an attack w/your bonded weapon. Add wis to damage later on (spotting weak points). Get the summon like Eldritch Knight at some point plus a tool prof? Look at Rangers for whirlwind attack.

Or you could lift the Battlemaster almost whole cloth and put it on a monk chassis. You'd just have to figure out what to drop for one of the archetype levels.