The Seven Great Demon Lords

In the Era of the Demon, seven demons who shouldn't have been were born on dates that shouldn't have existed. 

These seven demons were named by the great demon immortal, Munufie, as the Seven Great Demon Lords.

It was said their birth was an anomaly, but when the reigning Demon Kings discovered them, they banded together to banish them to purgatory.

Purgatory became their new home—though it was also their prison. However, it was said that the universe intervened before they were sent away, creating a way out for them.

The Seven Deadly Cards were crafted for their sake.

The first card is known as the [Abyssal Spire]. 

It is Maldrak's summoning card, the Abysswalker. He was Voidborn, a being whose true appearance remains unknown today—even to his parents.

He is one with the shadows, born from them. He carries the shadows with him whenever he moves, overpowering light and darkness.