Yu-Gi-Oh! Episode 204: "Makings of a Magician"
Zorc Necrophades (called Zorc the Dark One in the English dub) is a demon who inhabits the Shadow Realm. He serves as the central antagonist in the Dawn of the Duel arc, as well as the final and main villain of the Yu-Gi-Oh! anime, although he and Yami Bakura (a villain who appears often throughout the entire series) are really "one and the same."
Zorc appears as a large, purple-skinned demon with huge, curved horns, bat-like wings, and a large dragon/snake appendage between his legs. The dub changes this appendage to protrude from his chest instead of between his legs, due to its likeness to the phallus. In the bunkoban of the manga, it is made spiral around him, rather than point out suggestively. He is very similar in appearance to Diabound (albeit much larger and more demonic), which is possibly due to his connection to Thief King Bakura.
Zorc Necrophades was born eons before the Millennium Items were originally created (in the English anime, he is the creator of the Shadow Realm, and therefore predates the items, though they were made using his power). He was summoned by Akhenaden who brought all seven Millennium Items together in an underground crypt in Kul Elna village 3,000 years ago (5,000 years ago in the dub). When he is summoned by Akhenaden in the manga, he reveals to Pharaoh Atem that he was the one who manipulated Akhenaden to translating the Millennium Spellbook (the Millennium Tome in the manga) in order to be resurrected with the power of the newly made Millennium Items.
Zorc attempted to destroy the world, but was stopped by Atem. Atem sacrificed his life by sealing himself within the Millennium Puzzle and Zorc within the Millennium Ring. Zorc later resurfaces when he possesses Ryo Bakura as the villain Yami Bakura wishing to obtain all seven Millennium Items in order to resurrect himself. Eventually, when Atem wished to regain his memories, Yami Bakura turned the event into a shadow game played in the world of the pharaoh's memories, giving him a second chance to destroy the world. In this second face-off, the Pharaoh was able to destroy Zorc by combining the Egyptian Gods into The Creator God of Light, Horakhty. Before confronting Atem, Zorc had already defeated Exodia, the individual Egyptian God monsters, and Blue-Eyes White Dragon. This made him seem invincible until he was destroyed by Horakhty.