Building a duelist (in the sense of a dexterity combattant that uses a Dueling Sword) can be quite a daunting task. There are many relevant classes to consider when planning your leveling: Fighter, Aldori Defender, Rogue, Sword Saint, Duelist, Aldori Swordlord, even Monk or Paladin. Navigating through the feats they offer to pick the best can be quite tricky.

In this guide, we will start by discussing the strengths and weaknesses of duelists, so you can decide if they are for you in the first place. We will then propose 4 different builds for the archetype that you can use out-of-the-box in your game, or adapt to your style.

This guide assumes that you are already familiar with most of the in-game terms. They will be highlighted in bold for clariness. If some of them are unknown to you, don't panic: a quick internet search should resolve the situation.

Why chose a DEX based fighter rather than a regular STR one? Short answer is because it's cool. Long answer, we will discuss advantages and drawbacks below.

• Makes the most of your dexterity attribute for both attack (BAB, damage) and defense (AC, reflex). Further in the game, this makes any upgrade of your DEX very good.
  
• You'll rely on light armor (or no armor), freeing those juicy heavy armors for your other characters.
  
• Not wearing any armor qualifies you for other sources of AC: spells like Mage Armor or Shield (+8 AC total), or Monk AC bonus
  
• You will have high mobility due to light encumbrance. This mean tactical flexibility during your encounters.
  
• You can be extremely effective with the Trip feat !

• The archetype is very feats demanding. You'll need one for applying DEX to AB, another for applying DEX to damage, a third for applying DEX to Combat Manoeuvers, a fourth for using the exotic Dueling Sword itself, and even a fifth to qualify the Dueling Sword to the Duelist class (yes I know, it's weird). Fortunately those feats can be acquired at low cost with a good leveling plan and a careful multi-classing.
  
• You'll be very vulnerable to being flat-footed, as it makes you lose your DEX and Dodge bonuses to AC. Being flat-footed can sometimes be avoided with careful engagement. But it will still happen on a regular basis when you get ambushed. Don't disregard it.
  
• You'll be very vulnerable to Control spells that trigger a Will Save (example: Hold Person) as you may lose all you DEX and Dodge bonuses to AC. Most of the classes you'd consider hardly gives you any Will Save, the exception being the Sword Saint. That's why taking 1 lvl of Traditional Monk or 1-2 levels of Paladin is a consideration, as their associated Will Save boost is far from negligible !
  
• More fragile than a regular fighter. Because you have to multiclass into non-combattant class and don't have a lot of spare attribute points for C ON, you will be a little bit on the low side hp-wise.

The Dueling Sword is a very unique weapon in the game. An interesting but also fairly complicated one.

• Firstly, it has its own dedicated feats (Aldori Dueling Mastery) and classes (Aldori Defender, Aldori Swordlord).
  
  
• Secondly, it is considered an Exotic Weapon, meaning that you need the dedicated Exotic Weapon Proficiency (Dueling Sword) to be able to use it. Aldori Defenders get this feat for free at level 1, and Sword Saint are exempted from taking this feat if they choose the Dueling Sword as there Favorite Weapon. For this reason it's generally a good idea to start off as either of these classes.
  
  
• Thirdly, there are three ways to apply DEX to damages with this weapon, and they are not equivalent.
  The best two ways is to take either 3 levels of Rogue or 1 level of Aldori Swordlord. This way, while your off-hand is free, you will be considered wearing both a one-handed and a two-handed weapon. For example, it means that you could still get the +2 shield bonus of Aldori Dueling Mastery, while enjoying +150% DEX to your damages, and +3 damages with Power Attack (instead of the regular +2). I don't think there is any other finesse weapon that would allow you to do that.
  The lesser way to apply DEX to damages is to take the Slashing Grace feat. This would consider your Dueling Sword as one-handed (hence not applying bonuses to your damages).
  
  For this reason, the go-to choice is to take some levels of Rogue or Aldori Swordlord when possible. There is one notable exception concerning the Sword Saint: because of the Spell Combat class feat, his dueling sword will always be considered one-handed whatever the situation. In this special case, the Slashing Grace feat is the better way to apply DEX to damages since investing in Rogue or Aldori Swordlord would be overkill.
  
  
• Fourthly, a Dueling Sword is not a light nor a piercing weapon, hence shouldn't qualify for the feats of the Duelist class, but yet it does if you take special feats (Aldori Dueling Mastery or Slashing Grace).

As a side note, Aldori Dueling Mastery (special feat unlocked by the Dueling Sword) is a pretty bad skill. +2AC as shield bonus is inferior to what you would get from the 1st lvl spell Shield (+4AC), and those bonuses are not stackables. Consider taking it only for the +2 to Initiative (still inferior to the +4 granted by the Improved Initiative feat) when applying to the Duelist class.

In the following sections, I will propose 4 very different builds for your duelist: the Devious Officer, the Skirmisher, the Armored Dandy and the Aldori Fencer. Each of them makes the best of a specific mechanic, and involves a lot of multi-classing.

Role: melee support

This build is designed to take advantage of the capacities of the Aldori Swordlord prestige class.
The Devious Officer is a support melee fighter that deploy nasty tactics against his ennemies. He applies various debuff to his opponents, and mark them for almost instant death. His adaptive tactics makes him a suited fighter against both single targets and packs of ennemies. He starts the game as a glass cannon but will get more and more tanky, allowing him to stand on the frontline after the first levels.

TIP: As a support fighter, this build works best in a team with at least 2 other melee fighters that hit +3 DEX at lvl 12 (Valerie and Amirie are perfectly suited). This enables to trigger a lot of opportunity attacks from Trip and Combat Reflex feats.

End build: Fighter (Aldori Defender) 2 / Monk (Traditional Monk) 2 / Rogue (Thug) 4 / Aldori Swordlord 9

Race: Human (DEX +2)
Alignment: Lawful


For the rest of the game, just max DEX up to 24.

STR is at 9 because not needed combat-wise nor save-wise. I wouldn't hamper this attribute more because you still want to carry some items while at light encumbrance.
DEX is as high as possible
C ON gives a nice survivability boost with HP and fortitude saves to compensate for your early game as a Rogue.
INT is at 13 to grab Combat Expertise
WIS is at 14 to help with Will saves and to allow +2AC thanks to a level of Monk
CHA is not hampered because we will be doing a lot of Persuasion and Use Magic Device checks.

Important Skills:
Mobility 3 for Aldori Swordlord prerequisites + fighting defensively
Knowledge (World) 3 for Aldori Swordlord prerequisites
Persuasion: As high as possible for frightening opponents. Lvl 5 is also an Aldori Swordlord prerequisite
Perception: As high as possible for getting combat bonuses from Aldori Swordlord feats + this skill is just very good in the game
Use Magic Devices: As high as possible for using wands throughout the game (Wand of Mage Armor and Wand of Shield are important early)

Stats to boost with items/spells: DEX, WIS

Lvl 1
Fighter (Aldori Defender) 1: Combat Expertise + Trip + Agile Manoeuver

• You can't touch anything nor deal decent damages through regular attacks, but you make it up by being already competent at tripping. A tripped target suffer -4AC and -4AB and provokes attacks of opportunity when getting up. Abuse it with auto attacks and make sure you have an ally nearby.

Lvl 2
Rogue (Thug) 1

• Grants you Weapon Finesse for + 5 AB, Sneak Attack 1 makes up for your lacking DPS with a 3.5 damage bonus on average.
  
• Being a Thug rather than a regular Rogue will later allow you to frighten and sicken your ennemies.

Lvl 3
Monk (Traditionnal Monk) 1: Crane Style + Fury's Fall

• By activating Defensive Fight, you now trade +4AC for -2AB.
  
• +2 Will save is very nice
  
• At this level you should have access to a wand of Mage Armor (buy it to Bokken). It enables you to drop your light armor and benefit from +2AC granted by your WIS
  
• With Fury's Fall you now add twice your DEX for tripping an opponent, making you succeed reliably

Lvl 4
Rogue (Thug) 2: Weapon Focus (Dueling Sword), +1 DEX

• Better AB, damages, AC and trip. Yay !

Lvl 5
Rogue (Thug) 3: Outflank

• Your companions should get Outflank at the same level for +2 AB and attack of opportunities potential
  
• You get better Sneak attack an apply +150% DEX to damages.

Lvl 6
Rogue (Thug) 4: Dazzling Display

• This Rogue level is very important as it grants you Uncanny Dodge that makes you immune to losing your DEX AC bonus while flat-footed.
  
• Also makes you chose a bonus against your target, I prefer -2AC for a total of -6AC once tripped.
  
• Dazzling Display is usefull when swarmed by ennemies: it will make some of them flee (frightened) and the rest will be debuffed (shaken).
  
• Against a smaller number of ennemies, tripping is generally more effective.

Lvl 7
Fighter (Aldori Defender) 2: Combat Reflexes + Greater Trip

• Your companions should get Combat Reflexes at the same level
  
• Greater Trip now doubles the number of attacks of opportunities against your target

Lvl 8
Monk (Traditional Monk) 2: Dodge, +1 DEX

• This level of Monk is basically for the bonus feat Dodge as a Crane Wing prerequisite. +1 on all saves is decent too.

Lvl 9
Aldori Swordlord 1: Crane Wing

• +4AC is too good to pass
  
• The first level capacity is unfortunately wasted as we apply DEX to damages since lvl 5, but there's no way around it as you want your 4th rogue level for Uncanny Dodge anyway

Lvl 10 to 17
Grab the 9th level of Aldori Swordlord. Recommended feats are: Blind Fight,
Improved Critical, Seize the Moment, Crane Riposte and Piranha Strike

It's up to you for the last levels but I'd suggest grabbing another 3 levels of Aldori Defender, making it up to level 5 for Weapon Training. Alternatively, if you skipped Piranha Strike, you can take 3 levels of Slayer to grab Power Attack as a Menacing style feat and an additional Sneak Attack.

Role: backstabber

This build is designed to take advantage of the capacities of the Duelist prestige class.
The Skirmisher is a lone fighter that will take advantage of his high mobility and his damage output to quickly get rid of the ennemy backline. His defensive abilities are on par, and he can save your own backline should it get compromised. Although having some defensive perks, he should avoid the main frontline when possible: this is not where he shines.

TIPS:

• You will get high bonus to AC against opportunity attacks: use it to run aggressively toward the ennemy backline, or to defend your own companions. To do so, just trigger the Attack of Opportunity of the threatening mob with the Skirmisher before disengaging your companion away from the melee. Most ennemies have only 1 attack of opportunity per round, so the Skirmisher will take the blow for himself.
  
• Speed is key ! Abuse Expeditious Retreat and Haste later on.

End build: Monk (Traditional Monk) 1 / Magus (Sword Saint) 8 / Duelist 10

Race: Human (DEX +2)
Alignment: Lawful



Later, upgrade DEX to 20, then INT to 20

STR is at 9 because not needed combat-wise nor save-wise. I wouldn't hamper this attribute more because you still want to carry some items while at light encumbrance.
DEX is as high as possible
C ON is at a nice 14
INT is at 16 to take advantage of the Magus and Duelist capacities
WIS is at 12, it's more than sufficient because Magus have good Will saves
CHA is as low as possible, it's not a necessary stat in this build

Important Skills:
Mobility having a high score is nice to avoid being entangled by your Web spell.
Perception: As high as possible for it is just very good in the game
Use Magic Devices: As high as possible for using wands throughout the game (Wand of Mage Armor and Wand of Shield are important early)

Stats to boost with items/spells: DEX, INT, WIS

Lvl 1
Magus (Sword Saint) 1: Favorite Weapon (Dueling Sword) + Weapon Finesse + Slashing Grace.

• Important spells: Expeditious Retreat + Shield
  
• Because you chose Dueling Sword as your Favorite Weapon, you don't need to pick the related Exotic Proficiency feat and automatically gain Weapon Focus(Dueling Sword).
  
• You are already decent at touching and inflict good damages.

Lvl 2
Monk (Traditional Monk) 1: Crane Style

• Monk just have too much to offer. Crane feat line is great !

Lvl 3
Magus (Sword Saint) 2: Dodge.

• Dodge is not that interesting in itself, but is a small step toward Duelist prerequisites

Lvl 4
Magus (Sword Saint) 3: Wand Wielder, +1 DEX

• Wand Wielder enables you to cast your defensive spells in combat if ambushed, without losing dedicated turns.

Lvl 5
Magus (Sword Saint) 4: Piranha Strike

• Important spells: Web + Cat's Grace
  
• Web is a pretty nasty spell that grant you control of the battlefield. Your Duelist levels will later help you to not suffer from penalties.

Lvl 6
Magus (Sword Saint) 5: Combat Mobility

• You now have a much easier time dodging to the ennemy backline

Lvl 7
Magus (Sword Saint) 6: Crane Wing + Arcane Accuracy

• More defense
  
• Arcane Accuracy allows to apply your INT modifier to your attacks

Lvl 8
Magus (Sword Saint) 7. +1 INT

• Important spells: Dispell magic + Displacement (Haste is important as well but should be provided by other casters)
  
• We got 2 importants class feats at this level, one that granted us 4 levels of Fighter regarding feat selection, and another that added our INT bonus to initiative (hence lowering our chances to be caught flat footed)
  
• Dispell magic is to debuff your targets when they protect themselves with concealment or other magical means.

Lvl 9 to 19
Just get these Duelist levels ! Important feats (get them in any order): Weapon Specialization (Dueling Sword), Improved Critical, Crane Riposte, Combat Expertise.
I would then consider Critical Focus + Tiring Critical, Outflank, Seize the moment, Cornugon Smash (if you invested in Persuasion) or Hammering the Gap. It's up to you really.

Role: tank/frontliner

This build is designed to maximize defenses while not compromizing offensive power too much.
Who said you couldn't marry the elegance of a duelist with the classiness of wearing a 50kgs full plate armor ? The Armored Dandy is a frontline tank that will fight with a dueling sword and his off-hand free. It's a fairly solid build with good hp and saves. Early on, it is also less vulnerable to being flat-footed than the other builds, because the armor bonus still applies in this case.
This build offers the most regular and straightforward Fighter experience amongst the builds we proposed.

End build: Monk (Traditional Monk) 1 / Aldori Swordlord 1 / Fighter 18

Race: Human (DEX +2)
Alignment: Lawful


Later, upgrade DEX up to 22 and the last point can go in either WIS or CHA

STR is at 16, mostly to enable carrying a full-plate armor while still sitting at light encumbrance. Also allows for the power attack feat line and decent damages early game.
DEX is at a nice 18: no need to upgrade your DEX too fast as your AC bonuses will be limited by your Fighter levels anyway.
C ON is at a low 14 (16 or higher would be preferable for a tank but choices have to be made...)
INT is at 13 to allow for Combat Expertise
WIS is at 11, it's ok as Armed Bravery will catch up our Will saves
CHA is as low as possible. While you will be doing some persuasion checks, a slight malus is acceptable for such a a side mechanic.

Important Skills:
Mobility 3 is minimal for Aldori Swordlord prerequisites, but having a higher score is nice
Perception: As high as possible for it is just very good in the game
Persuasion: As high as possible, we will be doing persuasion checks
Use Magic Devices: Some points are desirable for using wands (notably the Wand of Shield)

Stats to boost with items/spells: DEX

Lvl 1
Fighter 1: Exotic Proficiency (Dueling Sword) + Weapon Finesse + Power Attack

• You are already decent at touching, and have a nice damage output.

Lvl 2
Monk (Traditional Monk) 1: Crane Style

• Some added defensive capabilities from the start

Lvl 3
Fighter 2: Weapon Focus (Dueling Sword) + Dodge

• regular power up. Dodge is just a prerequisite for Crane Wing

Lvl 4
Fighter 3: +1 DEX

• Now wearing medium armors without movement penalties

Lvl 5
Fighter 4: Crane Wing + Dazzling Display

• Dazzling Display is necessary for Aldori Swordlord. Furthermore, it's a useful capacity to have, as a tank is by definition in the middle of the battle and well positionned for affecting the maximum number of opponents. You will later deepen into the feat line by grabbing Dreadful Carnage and Shatter Defense

Lvl 6
Aldori Swordlord 1:

• Now applying +150% DEX to damages

Lvl 7
Fighter 5: Weapon Specialization (Dueling Sword) + Weapon Training(Heavy blades)

Lvl 8
Fighter 6: Combat Expertise, +1 DEX

Lvl 9
Fighter 7: Crane Riposte

• Now wearing heavy armors without movement penalties

Lvl 10
Fighter 8: Improved Critical

Lvl 11
Fighter 9: Greater Weapon Focus (Dueling Sword) + Armed Bravery

• Armed Bravery will provide a ton of Will save bonuses throughout your progression

Lvl 12
Fighter 10: Cornugon Smash, +1 DEX

Lvl 13
Fighter 11: Blind Fight

Lvl 14
Fighter 12: Greater Weapon Specialization

Lvl 15
Fighter 13: Penetrating Strike + Combat Manoeuver Defense

Lvl 16
Fighter 14: Dreadful Carnage, +1 DEX

Lvl 17
Fighter 15: Shatter Defense

Lvl 18
Fighter 16: Greater Penetrating Strike

Lvl 19
Fighter 17: Improved Blind Fight + Trained Initiative

Lvl 20
Fighter 18: Critical Focus, +1 WIS or CHA

Role: Frontliner

This build is designed to take advantage of the disarm feat of the Aldori Defender.
The Aldori Fencer is a frontliner with defensive and offensive capacities, who specialized himself in disarming his opponents.
As a disclaimer, I must say that this build feels like a weaker version of the Devious Officer. The reasons are two-fold. Firstly, disarm works only against armed opponent, while trip works against almost anything (even giant slugs !). Secondly, disarm lacks an equivalent of the Fury's fall feat, that would make the mechanic work consistently.
Anyway, since the disarm mechanic is encouraged by both the Aldori Defender and the Aldori Swordlord classes, it deserves its place in the guide and we will try to make it work !

End build: Monk (Traditional Monk) 2 / Fighter (Aldori Defender) 6 / Aldori Swordlord 9

Race: Human (DEX +2)
Alignment: Lawful


Later, upgrade DEX up to 22 and the last point goes in CHA

STR is at 13 to enable Power Attack and help a little bit in the early game
DEX is as high as possible.
C ON is at an acceptable 14
INT is at 13 to allow for Combat Expertise
WIS is at 14 to help with Will saves and gives a little bit of AC with the Monk level
CHA is at 9. You will do persuasion checks but a -1 is still acceptable.

Important Skills:
Mobility 3 is minimal for Aldori Swordlord prerequisites, but having a high score is nice to stay mobile on any terrain.
Perception: As high as possible for it is just very good in the game
Persuasion: As high as possible, we will be doing persuasion checks
Use Magic Devices: As high as possible for using wands (notably the Wand of Mage Armor + the Wand of Shield)

Stats to boost with items/spells: DEX, WIS

Lvl 1
Fighter (Aldori Defender) 1: Weapon Finesse + Combat Expertise + Power Attack

• You are already decent at touching, and have a nice damage output.

Lvl 2
Monk (Traditional Monk) 1: Crane Style

• Some added defensive capabilities from the start

Lvl 3
Fighter (Aldori Defender) 2: Disarm + Agile Manoeuvers

• There you go, you can disarm !

Lvl 4
Fighter (Aldori Defender) 3: +1 DEX

Lvl 5
Fighter (Aldori Defender) 4: Weapon Focus(Dueling Sword) + Dazzling Display

Lvl 6
Aldori Swordlord 1

• 150% DEX to damages

Lvl 7
Fighter (Aldori Defender) 5: Greater Disarm

Lvl 8
Fighter (Aldori Defender) 6: +1 DEX

• You grabbed the Aldori Defender special disarm feat. To better your disarm line you must now take Aldori Swordlord levels

Lvl 9
Monk (Traditional Monk) 2: Dodge + Crane Wing

• Casually grabbing +5 AC feels right

Lvl 10 to 17
Aldori Swordlord 2 -> 9. Important feats are (grab in any order): Shatter Defense, Crane Riposte, Improved Critical, Combat Reflexe
For the end levels I would advise to rank up Aldori Defender to level 8 for unlocking the Fighter feats, and then to take the last level of Aldori Swordlord

I hope you enjoyed this guide about duelists. Feel free to experiment your own builds, and if you come up with something interesting yourself, don't forget to share !

Have a great day and a nice game.

• corrected a mistake about DEX to damages concerning the Sword Saint. Updated A word about the Dueling Sword and related feats and Build - Duelist - The Skirmisher sections in consequence.
  
• added a paragraph about Exotic Weapon Proficiency (Dueling Sword) in A word about the Dueling Sword and related feats