Blademaster

While others were busy expanding their versatility of multiple weapons - you studied the blade. While others learned to craft various things - you studied the blade. While some of your fellow fighters even dabbled in magic - you studied the blade. And the blade now repays you. Your defensive and offensive capabilites are honed, pushing the limit of what is pure phsyically possible with a sword in hand. And they shall be pushed further, for you keep studying the blade.

For clarification
For mechanical reasons the following weapons count as swords for the purpose of this class:

• Shortsword
• Longsword
• Scimitar
• Rapier
• Greatsword
• Double-Bladed Scimitar

Any weapon not listed above is not eligible for the features of this class.

Know Your Blade

Every sword is unique. And so is every wielder. To better understand their chosen tool, blademasters learn how to shape them. It is said that true blademasters only wield swords they smithed themselves.

When you choose this subclass at level 3, you gain proficiency with smith's tools. Also, your proficiency bonus is doubled for any ability check you make that uses smith's tools in relation to swords. (For example when you craft a sword.)

A River To Rain

To cut is not only to harm. With enough skill a sword offers just as much protection as any shield. When you choose this subclass at level 3 you learn how to reduce damage dealt to you.

If you are wielding a sword, you can use your reaction to deflect the incoming strike when you are hit by a melee attack. When you do so, the damage from the attack is reduced by 1d6 + your strength modifier + your proficiency bonus.

If you are wielding a sword with the finesse trait, you can use your dexterity modifier in place of your strength modifier when calculating by how much you reduce the damage. 

When you reach certain levels in this class, the number of die you roll to determine how by much the damage is reduced increases: to 2d6 at 7th level, to 3d6 at 10th level and to 4d6 at 15th level.

"You cannot halt a river. But even the strongest stream can be dispersed into a gentle sprinkle." - Moria

Deep Cuts

The precision with which you handle your sword lets you cut deeper and cause more harm.

Starting at 7th level, when you hit with a melee weapon attack made with a sword, you can roll an additional weapon damage die when determining damage. This additional die does not get doubled from crit until you reach level 15 in this class.

You can use this feature a number of times equal to twice your proficiency bonus. You regain all spent uses when you finish a short or long rest.

When you reach level 18 in this class, you get to roll two additional die when using this feature.

Blademasters Domain

While in a fight, your martial prowess and immense skill with the blade, lets you rule over the immediate surroudings.

Starting at 10th level, as a bonus action you can enter a stance granting you the following benefits:

• In a sphere of 10 feet around you, you gain blindsight and your attacks can reach any target within.
• When something enters the sphere, you can use your reaction to make an opportunity attack against it.
• You cannot be forced to make attacks at disadvantage.

The stance lasts for a number of turns equal to your proficiency bonus.
You can use this bonus action only if you haven’t moved during this turn, and after you use the bonus action, your speed is 0 until the end of the current turn. Your movement speed is also halved while you are in this stance. 
You can enter this stance a number of times equal to your proficiency bonus and regain all expened uses when you finish a short or long rest.

Turn The Tide!

Starting at 15th level, if you are wielding a sword and an enemy within 5 feet lands an attack against you by meeting your AC exactly, you can use your reaction to turn the blow aside taking no damage and perform a devastating counter. As part of the same reaction you can make a melee weapon attack with a sword. On a hit the attack automatically becomes a critical strike.

If Blademasters Domain is active, the range from within which the triggering attack has to come from increases to 10 feet.

You can use this feature a number of times equal to your proficiency bonus and regain all expended uses when you finish a short or long rest.

When you reach level 18 in this class, this feature also triggers, when an enemy misses your AC by one. 
(For exampl: if your AC is 19, attack roll of 18, 19 and 20 trigger this feature.)

"Meets does not beats!" - Hänsel

Honing The Blade's Master

Upon reaching level 18 in this class you gain the following benefits:

• Your Deep Cuts ability gains an additional weapon damage die.
• The reaction you get from Turn The Tide! also triggers if the enemy attack roll is one below or above your Armor Class.