Samurai will be similar to knight in that he has code some kind, lawful oriented also. But unlike knight samurai is less 'jack of all trades' combatant (as knight gets lots
bonus feats), samurai is more specialized and they get also Ki sort special abilities and so samurai has more mystic martial powers (approaching bit like a monk). Samurai term can be replaced with weaponmaster, kensai, warlord or champion.
Samurai looses following class features; Two Swords as One, Laijutsu Master, Improved Initiative, Improved Two Swords as One, Greater Two Swords as One.
Samurai gains new features and also they get 4 skill points per level instead two. They also get Spot and Listen as class skills.
1st: Daisho Proficiency is translated to 'Exotic Weapon Proficiency'. In short samurai gets to choose proficiency to any single exotic weapon from following list; Katana (bastard sword), Naginata (greatspear), Greatbow, Tetsubo (Warmace) or Double-Bladed Sword (or any double weapon). Choosing their trained proficiency with exotic weapon serves as guideline for later abilities they gain with their chosen weapon. Samurai gains class feature known as Courtly Knowledge
, it functions as Bardic Knowledge but it's based not to rumors or legends but on various little facts. It allows samurai use this knowledge to gain information regarding country customs, country geography (important sites only), rulers, about metropolis scale cities, noble families (can substitute a K:nobility&royalty roll albeit less accurate), military history, art and warfare. It also applies identify any legendary warriors/generals.
Also they gain class feature known as Code of Bushido
(honor code based on seven virtues), it works same as paladin code of conduct to determine samurai's behavior and breaking the code will cause samurai loose all class features expect related to their weapon mastery, base attack, HD, weapon proficiencies and saves and skill ranks. Code is in below;
2th: Samurai gets first Weapon Mastery feature, which is either a feat or ability associated with weapon of their choice what they picked in 1st level. Samurai get in 6th, 10th, 14th and 18th levels additional weapon mastery features. Below is details for 2th level;
-Laijutsu Training (katana): You get Quick Draw feat for free (applies to all weapons) and gain +2 to initiative score.
-Firm Grip (Naginata): You gain weapon focus with Naginata (or any polearm) and get +2 resist disarm and sunder checks.
-Archery Training (greatbow): You get Point Blank Shot feat for free and gain +2 bonus to crit confirmation rolls with archery attacks.
-Crushing Force (tetsubo): You gain power attack feat for free and ignore -2 hardness/DR on any objects/creatures you attempt break.
-Dancing Steel (double-bladed sword): Gain two-weapon fighting and gain +2 shield bonus to AC when doing full attack with chosen double weapon (stacks with any feats which provide shield bonus to AC).
3th: Kiai smite can be applied with any weapon attacks (even with weapons which were not their chosen weapons). Also they gain feature called Zen Focus which allows add charisma modifier to all saves with Kiai Smite. Instead channeling Kiai Smite to fierce attack they can channel it as immediate action to improve their saves until start of their next turn. Also your number of Kiai smites is Cha Mod + 1/3 of your level (can with feat get +2 extra Kiai smites).
4th: Samurai gains class feature known as Unbending Resolve, it allows re-roll any will saves against fear and gives +4 bonus to will saves against fear. However samurai who succumbs to fear effect will loose this class feature and gains -2 penalty to attack, damage and saves until he somehow redeems himself (resisting a fear effect without this class feature always qualifies as form of redemption).
6th: Weapon Mastery;
-Laijutsu Mastery (katana): You gain improved initiative feat.
-Swift Hands (Naginata): You gain combat reflex feat.
-Eagle Eye (greatbow): You gain Far Shot feat.
-Shattering Force (tetsubo): You gain Improved Sunder feat.
-Blur of Steel (double-bladed sword): You gain improved two-weapon fighting feat.
8th: Samurai gains Death before Honor feature, it gives Samurai benefit of Diehard feat and also while acting under 0 HP they do not loose HP doing standard or full round actions. Also they gain unlimited use of Kiai Smite class feature at 20th level while under 0 HP.
10th: Weapon Mastery;
-Laijutsu Strike (katana): You gain sneak attack ability (which value is same as if samurai levels would be rogue levels) only if you perform single standard attack against single flat-footed foe and do it through drawing katana from scabbard as free action. Samurai can qualify for any Ambush or feats which enhance sneak attack.
-Power Thrust (Naginata): When you charge (either mounted or on foot) and hit with charge attack with your polearm, you can perform a free trip attack against opponent and you gain +4 bonus on the contested roll. on failure you do not loose your weapon.
-Zen Shot (greatbow): Instead gaining usual benefits of Kiai Smite, you can instead make Zen Shot which you perform as full round action. The shot targets touch AC of the target and multiplies damage equal to number of potential attack you gave up + 1 (meaning if you got +11 BAB and thus giving up three attacks, your bow damage is multiplied by four).
-Destroying Force (tetsubo): Your attacks ignore now -5 hardness/DR from any objects/creatures.
-Dazzling Display (double-bladed sword): As you perform full attack with double weapon and instead taking normal benefits of Kiai Smite, you gain 50% concealment until start of your next turn. Does not count as cover for hiding.
Also in 10th Samurai gain class feature known as Daimyo; they become influential governors of a large piece of land and followers which are their bannermen and loyal servants. Daimyo answers only either himself or superior sovereign (like shogun, king/queen or other similar figure). Gaining a leadership feat with +5 bonus to leadership score, they gain Landlord feat from stronghold builder's guide and he gains half of his class levels as bonus to diplomacy and intimidate skill rolls.
12th: Chi Shout; Samurai can 1/day generate Heroism (greater) spell (his samurai class levels counting as CL) as a supernatural effect as standard action. He can do the inspiring shout additional times per day at 16th and 20th level.
14th: Weapon Mastery;
-Unseen Strike (katana): Instead normal benefits of Kiai Smite you can make your Laijutsu Strike (gained in 10th level) a extraordinary invisible attack. Target does not need be flat-footed to use this technique and so as attack is invisible, most foes are flat-footed and thus receive sneak attack damage from doing laijutsu strike.
-Dancing Heaven Spear Dance (Naginata): You gain Short Haft feat and also while doing full attack with polearm you get dodge bonus equal to total number of attacks you make in round and you can make a additional attack with -5 penalty but it does 1d8 damage (20/x2 crit) and it's bludgeoning damage with butt end of the spear (but any enchantments in other end of spear applies to other end as well).
-Sharp Shot (greatbow): You gain Improved Point Blank Shot feat for free.
-Singing Thunder Strikes (tetsubo): When your second attack hits with full attack, target must roll fort save DC 10 + Cha mod + dmg done with attack or become fatigued for rest of encounter, if third attack hits (and target is fatigued), it needs roll same save or become exhausted and if fourth attack hits (and target is exhausted) they need roll same save again or become knocked out unconscious. This ability does not work those which cannot become fatigued nor exhausted or are immune to critical hits.
-War Dance of Blades (double-bladed sword): Now while doing full attack you can take 10'ft movement in between each attack. Distance covered cannot be greater than double your movement speed and every attack must strike different target. You provoke the usual AoO from your movement into or out of enemy squares.
16th: Unbending Resolve feature is upgraded into Legendary Resolve. It gives +4 to all saves and allows re-roll saves against fear, enchantment/charm, poison, stun, dazed, paralysis, fatigue, exhaustion and death effects.
18th: Weapon Mastery;
-Void Cut (katana): Instead normal Kiai Smite benefits you can perform Unseen Strike (gained in 14th level) but to any target in close range (like a spell) as supernatural ability.
-Void Wave Technique (Naginata): Instead normal Kiai Smite benefits you can perform double movement action where you charge on every foe in 15'ft wide line path. You perform melee attack against every foe in the line and every foe you strike you can perform overrun attempt (provokes no AoO) and you count charisma modifier times bigger while doing overrun attempts (so +3 modifier means your three times larger). If foes fail resist it, they fall prone on ground and you move over them. You can perform attacks of opportunity on every foe which fall prone before you.
-Void Shot (greatbow): While doing Zen Shot you gain effects of true strike spell and also attack ignores all DR/Hardness and you do maximum possible damage with the bow (including in critical hits if any).
-Void Hammer (tetsubo): Your attacks ignore now all DR/Hardness and instead normal Kiai Smite benefits you can attempt drain 1d4 levels from target (fort save DC 10 + class level + charisma mod negates) with a single attack which does maximum possible damage.
-Dancing Void Mastery (double-bladed sword): You gain greater two-weapon fighting feat and all attack penalties with using TWF line feats is reduced by -3. Also off hand weapon strike uses your full strength modifier instead half of it.
20th: Besides Frightful Presence samurai gains class feature called Shogun. They in essence become a ruling emperors in chosen domain; they gain +10 leadership bonus (does not stack with daimyo bonus) and gains second cohort and can use his full class levels in diplomacy and intimidate rolls.