The blades were renowned dragon hunters, and after the rise of the Septim Dynasty, became protectorates of the the Emperor and his family. They are well versed in combat with katanas, nodachis and unique crossbows that are especially powerful to take down dragons.

Their order was founded 125 years before the First Era, and they were all warriors hailing from the far east continent of Akavir. Dragons and subsequent dragon attacks were an unfortunate fact of life for the inhabitants of the continent. However, necessity bred invention, and the Blades were born. At the start, when dragon attacks hampered technological progress, the Blades were little more than a band of angry townspeople wielding farming tools and old weaponry from their ancestors. They were relatively unsuccessful in their attempts and as a result many villages suffered more casualties. Around this time however, Tiber Septim, or Talos, as his true Nord name was, conquered the neighboring continent of Tamriel, and his Imperial Armada were making for Akavir. 

The Empire set up their first outpost on the western tip of the island, near the village where the Blades were stationed. They had peaceful interactions, but they met the native dragons. Talos saw the people's daily struggle. For the following months, the Empire hunted the dragons, and wiped them all out, save for several that fled to unknown places. Finally, the Akavirians saw progress in weaponry, farming and education. Giant cities were built, schools were constructed, and the Blades rose to become the greatest fighting force ever seen in a long time. They usually wear a Japanese styled steel splint armor, and wield katanas, shields, nodachis, and specialized heavy crossbows that were designed to pierce dragon scales. 

Eventually, all the Akivirian dragons went away, and the Blades became the honored guard of the Emperor.

Improved Critical

Beginning when you choose this archetype at 3rd level, your weapon attacks score a critical hit on a roll of 19 or 20, and you score a critical hit on dragons on a roll of 18 to 20. (For dragons, just refer to creatures with the dragon type.)

Dragon Chaser

Starting at 7th level, you can double your speed when moving to dragons, and gain advantage on rolls to track them. You also gain advantage on attack rolls against dragons.

Blades Combat Training

At 10th level, you deal additional damage die against dragons, and you obtain Blades Armor, a Blades Shield, a Blades Katana and the unique Blades Dragon Harpoon.

The Blades Armor set is heavy armor that has a base AC of 17, gives you disadvantage on Stealth checks, and gives you resistance to fire damage, and it weighs 55 pounds.

The Blades Shield gives you a +2 to your AC, as well as giving you a resistance to fire damage of you hold it up. It cannot be wielded with ranged weapons or weapons with the heavy property, and it weighs 8 pounds.

The Blades Katana deals 1d8 slashing damage, has the light and finesse properties, and weighs 4 pounds.

The Dragon Harpoon is a unique heavy crossbow which deals  2d6 piercing damage, has the heavy and two-handed properties, and weighs 7 pounds. If the target is hit, it will grapple the creature, who must make Strength saving throws (DC=10+your Strength modifier) to be able to move out of your range. It has a range of 60/100.

Archery

You gain a +2 bonus to attack rolls you make with ranged weapons.

Defense

While you are wearing armor, you gain a +1 bonus to AC.

Dueling

When you are wielding a melee weapon in one hand and no other weapons, you gain a +2 bonus to damage rolls with that weapon.

Great Weapon Fighting

When you roll a 1 or 2 on a damage die for an attack you make with a melee weapon that you are wielding with two hands, you can reroll the die and must use the new roll, even if the new roll is a 1 or a 2. The weapon must have the two-handed or versatile property for you to gain this benefit.

Protection

When a creature you can see attacks a target other than you that is within 5 feet of you, you can use your reaction to impose disadvantage on the attack roll. You must be wielding a shield.

Two-Weapon Fighting

When you engage in two-weapon fighting, you can add your ability modifier to the damage of the second attack.

Superior Critical

Starting at 15th level, your weapon attacks score a critical hit on a roll of 18–20, and 17-20 on dragons. (Creatures with the dragon type).

Dragon Master

At 18th level, you have resistance to all damage dealt by dragons, have advantage on attack rolls, ability checks and saving throws against dragons, and you now you can engender fear in all dragons, regardless of their immunity to the fear status effect. All dragons in a 30 foot radius must make a DC 20 Wisdom check, or be frightened by you for the duration of 5 turns. the effect repeats if they get in that range again.