Dakkon was a blacksmith and warrior of renown.  He was approached by the planeswalker Geyadrone Dihada, who offered to make him a planeswalker if he would make her the most powerful blade in existence, the Blackblade. He agreed and she shared with him the secret sorceries required to make the sword a "soul-drinker", a blade capable of stealing the energy of those it killed. Dakkon claimed to have stood at his anvil every day for ten years, cooling the blade by killing a slave with it after each time he heated it. Finally the blade was completed, and Dakkon could not help but test it.

Dakkon waded into battle and, with each kill, felt his strength grow. So ferocious was his assault that as tales spread of his slaughter, his name became "Dakkon Blackblade". Dihada returned when she heard these stories and did make him a planeswalker, having sensed the spark within him when they first met but immediately afterwards she stabbed the sword into Dakkon's shadow and absorbed his soul but not his life. Dakkon was left wandering the plane, wondering why Dihada would grant him so much power, only to make him her enemy.

(the rest of the story can be read at the wiki: https://mtg.gamepedia.com/Dakkon_Blackblade)

The flavor of the deck:

Blackblade Reforged and a few tutors.  He made the weapon so it makes sense that he can aquire it easily.  Various cards that refer to forges and masterpeices were included due to his ability.

Creatures that can sacrifice themselves.  The Blackblade was made by killing a slave each day and I felt that using creatures that wanted to die to help Dakkon out was the best route for flavor.

Lots of removal.  Dakkon was a feared warrior and I feel that pointed removal is a good way to show his combat prowess.

Lastly some cards were chosen based on the name: Tragic Arrogance, Debt to the Deathless, Beseech the Queen, and Fractured Identity  because of lust for power causing his servitude to Geyadrone Dihada. He fights Chromium, thus the Elder Dragon's inclusion and Korlash, Heir to Blackblade gets in due to wielding the Blackblade.  The Amulet of Safety is the charm that keeps Carth safe from Dakkon's wrath while they try to kill Dihada.