Inferno (インフェルノ Inferuno) is the overarching antagonist of the Soul series as the final boss and main villain of the first three video games. He first appeared in Soul Blade under the name Soul Edge, he later appeared in; Soul Calibur, Soul Calibur II, Soul Calibur III: Arcade Edition and Soul Calibur: Unbreakable Soul. He also appeared in Soul Calibur V as a costume for Cervantes in Legendary Souls mode. He is playable in Soul Calibur II with the use of Action Replay and is available for play on both the original Dreamcast version, and the Xbox Live port of Soul Calibur. He returns as an unlockable character in Soul Calibur VI.
In Soul Calibur III: Arcade Edition, he is non-playable and the only NPC that can be fought before Abyss or Night Terror.
He is the controlling force behind Nightmare, possessing Siegfried in Soul Calibur and Soul Calibur II, and becoming the second incarnation of Nightmare in Soul Calibur III after Zasalamel creates an artificial body for him, allowing him to walk freely without needing a host.
He was eventually defeated when the armor was destroyed by Siegfried in the end of Soul Calibur IV. However, after seventeen years, a new Azure Knight rises through the host, Graf Dumas.
Inferno is the embodiment of Soul Edge’s will, an evil amalgam of all the warriors’ souls it has claimed. Nobody knows that it he wants exactly. Some say he just obeys his desire to fight, malm, and gather souls. The eerie fire that surrounds him is the result of all the souls the sword has reaped being burned to fuel.
Harvested from the souls it has collected, Inferno possesses a deep knowledge of all fighting techniques – allowing it to use any weapon style with a phenomenal degree of skill. Though its power defies standard means of measurement – it easily transcends that of any of its previous vessels. Although Inferno’s look changes with every incarnation, rest assured that it is stronger and more brutal than ever!
After Sophitia destroyed one of the two blades of Soul Edge and Cervantes was killed by Taki, the remaining sword was picked up by Siegfried, who was not in a right mind after killing his own father, Frederick. Inferno promptly made Siegfried his new host and they became Nightmare, unleashing the Evil Seed in the process. Assuming the identity of Frederick, Inferno easily tricked Siegfried into killing many innocent lives to resurrecting Frederick. But in reality, Soul Edge was regaining its power.
When Soul Edge was about to become fully resurrected, Nightmare was defeated by Kilik, forcing to abandon the Azure Knight and reveal its true form. Dragging Kilik and Xianghua into the Astral Chaos, Inferno fought the latter after her Krita-Yuga revealed itself as Soul Calibur. Despite losing the fight, Inferno caught a weakened Xianghua off guard but was thwarted by Kilik, who then fought the demon in his purified Malfested form. Inferno was weakened enough by Kilik and was then seemingly destroyed by Xianghua.
The result of that battle was that Soul Edge was now weakened again, and Siegfried was freed from Inferno's control. But the demon tried to corrupt the knight again until Soul Calibur cried for help, prompting Siegfried to take up Soul Edge and mentally enter the Astral Chaos. It was here that Inferno assumed Nightmare's form to mock him for his sins as the Azure Knight. After one battle, Inferno revealed his true form and attacked Siegfried again. In the end, Inferno could not consume Soul Calibur, but with Siegfried's consciousness trapped inside the Astral Chaos, the demon took control of his body and became Nightmare again.
He is voiced by Christopher Judge in the English dub and Jin Urayama in the Japanese dub.