The Archfiend is the ancient creature sealed within Mt. Fuji, the gateway to the underworld, which the four Greater Fiends, Alexei, Elizebet, Volf, and Zedonius are trying to revive under the guidance of Dagra Dai, the infernal high priest. With the aid of the Black Spider Clan, they are able to achieve their goal at the cost of their own lives, twice apiece.
In its infant stage, the Archfiend is just barely smaller than the Vigoor Emperor, of whose remains were used in the revival. In that stage, it appears as little more than a decaying blob with a glowing orb at it's center. When Ryu Hayabusa defeats the first form, he attempts to escape Mt. Fuji. A drop of blood from Ryu falls back to the depths of the underworld and hits the Archfiend. With a fury the beast is revived in it's final form, comparably around the same size of the Vigoor Emperor's largest form. Once again Hayabusa slays the deity, and the world rests at peace.