Blademaster

A samurai's katana swats arrows out of the air as he runs across the battlefield.  An orc chieftain twirls a singing great axe in graceful, fluid motion as she cleaves apart an entire garrison.  A flurry of blows and an imposing elf carves a hole through a stone wall with an elegant polearm.  These individuals are not mere warriors.  They are blademasters.

While tacticians and strategists would insist that different weapons have different uses in different situations, and as such, must be applied to suit the circumstances, a blademaster sees the limitations of their weapon as challenges to be overcome.  Training with a single weapon to utter exhaustion, a blademaster forges their reflexes and cunning just as much as their blade, pushing themselves to find any method through which they can apply the strength of their treasured blade.  The blademaster's technique is an expression of one's very being, the blade an extension of their essence, their skill embodying their own ability to overcome any challenge and meet any foe with steely resolve and cold precision.

Razor's Edge

Starting at 3rd level when you take this Archetype, choose a martial melee weapon type you are proficient with that deals Slashing damage and has the Two Handed or Versatile property to Master. When making attack rolls with this weapon you can add half your intelligence modifier (minimum of 1) to the attack rolls. If you attack with any other weapon, you subtract your intelligence modifier (minimum of 1) from the attack rolls. 

Whenever your class gains an ability score increase, you may switch your mastered weapon to a new weapon. 

You gain an additional mastered weapon at 10th level and then again at 17th level. 

Mastered Weapon

you master a two handed weapon that deals slashing damage 

Flashing Steel

Starting t 3rd level when you take this archetype, your reflexes are put to the test as you use your Mastered weapon to deflect harm more effectively than any shield.  While wielding your Mastered weapon with two hands and not wearing armor or a shield,  your AC becomes 10 + STR + DEX.

 

Uncanny Strikes

At 7th level, your technique is so flawless that you can perform feats of bladework that seem supernatural.  When wielded with two hands, your Mastered weapon counts as magical for the purpose of overcoming resistances and exploiting vulnerability.

Focused strikes

You now find it easier to to study your opponents and find weaknesses in battle.. at 10th level , while wielding your mastered weapon in two hands. you can use your bonus action, to attempt to exploit weakness’ in your enemies attacks, you can force the targeted creature to make a Wisdom saving throw (DC is 8+intelligence+prof). On a failure you may add half your intelligence modifier (minimum of 1) to all damage rolls against that creature. 

once you use this ability you cannot use it again until you finish a long rest 

at 20th level you gain an additional use of this ability. 

Standing Firm Against All Odds

You become the pinnacle of defensive battling. as a reaction you, while wielding a mastered weapon in two hands,  can  add half your constitution  modifier to your AC. you can use the feature a number of times equal to your proficiency bonus.   

Bladestorm

 

At 18th level, you hone your technique to true perfection, and can unleash a devastating whirlwind of strikes at a moment's notice.  Whenever you make a melee weapon attack with a Mastered weapon you are wielding with both hands, you may apply the attack and damage rolls to all enemies are in range of your melee weapon attack.

you can use this 3 times before needing a short rest to use it.