At one time, Nightmare committed countless cold-blooded murders while under the control of Soul Edge.
All who knew of him feared his crimson gaze and his strange, one-eyed, giant blade.

Originally, Siegfried Schtauffen was the leader of a group of brigands known as the Black Wind, whose stronghold was located in the Black Forest near the Roman Empire.
It was news of his father's death that drove him from his marauding lifestyle, resolving to find his father's killer.
Hearing word of a sword known as Soul Edge, he became convinced that he could slay his father's murderer if he found this ultimate weapon.
He searched through the battlegrounds in every region he traveled.
Eventually, he came across a sword in a Spanish harbor that emitted a strange aura beside the corpse of its owner, who appeared to be a pirate.
The dead body returned to life, covered in flames, as if to protect the sword.

Upon defeating the apparition, he reached for the hilt of the mysterious blade.
It was then that he heard the voice of Soul Edge, the sword that feeds on souls.

It told him that if he used the souls absorbed by the sword, he would be able to resurrect his father.
Accepting his new goal, the man's body began to surge with the evil energy of the sword.
The energy became a beautiful pillar of light that pierced the evening sky and dissipated into the atmosphere.

From that moment on, the man became Nightmare, the evil knight who would strike fear into every corner of Europe.

Having determined that the power Soul Edge had at that moment was insufficient to revive his father, Nightmare attacked village after village to nourish the blade.
Not satisfied, he sought out those with strong souls to feed the evil sword.

The killings ended three years later, when Nightmare came across three sacrifices for his blade.
One of them wielded a spirit sword called Soul Calibur, which possessed an aura that was the polar opposite of the evil power emitted by Soul Edge.
The battle between the swordsmen took place in a vortex of hellfire and evil energy summoned by Soul Edge.
After a raging battle, the evil sword shattered, and both Nightmare and Soul Edge fell into the collapsing void.

With Soul Edge severely weakened, Nightmare regained some of his humanity.
Along with lucidity came the horrifying memories of the sins he committed, as well as the fear and anger of those who were slaughtered by him.
Moreover, he realized that he had been the one who murdered his father.

Expelled from the void into an unfamiliar place, Nightmare disappeared into the night-the evil sword still in his grip.
Soul Edge was weaker now, and splinters of itself were left in Nightmare's footsteps.

He knew Soul Edge must never fall into the hands of another man.
He set off to go as far away as possible from human settlements.

Yet each morning, he awakened to the sight of people slain by him during the night.
While he slept, Soul Edge took over his mind and flesh, and he was burdened by this new guilt.
Nevertheless, he did not choose to take his own life and end things easily. He knew that if he died, the sword would only find a new host to continue its evil ways.
The only solution was to find a place where the evil could be imprisoned forever.

Initially, the balance of power between him and the sword were equal.
As time wore on, his control over his body became irregular, and the sword held sway over him for slightly longer periods of time.

The number of those who fell victim to the blade continued to grow.
The sword healed itself gradually by feeding off the victims' souls.
After four years, the sword had nearly recovered to full strength.

The fragments of itself lost during its escape ... The evil energy dispersed as the Evil Seed … Soul Edge's shattered companion blade … the other Soul Edge ...

With dominant control over its host body, Soul Edge, once again in the form of "Nightmare",  began to pursue the fragments of itself that it had lost.
It was on a quest to restore itself completely !

At the same time, he continued to fight the evil sword's plans with the little sanity left within him.