Dartz is the main antagonist of Season 4 of the Yu-Gi-Oh! anime, Waking the Dragons. He lives in the ancient city of Atlantis, and is the father of Chris and son of Ironheart. His entire arc is filler, and therefore anime-only.
Dartz was turned evil by the power of the Orichalcos, making him believe that mankind was evil, and served the Orichalcos's master, the Great Leviathan, and planned to awaken him by using Orichalcos cards to steal souls from victims to feed to him. Disguising himself as Gozaburo Kaiba, he kidnapped Alister's brother Mikey (killed in the Japanese version), framed Valon (paid a gang to burn down the church Valon lived in, in the Japanese version), and caused a ship Rafael was on to crash into a typhoon (which killed Rafael's family in the Japanese version), making them work for him. He dueled Yami Yugi and Kaiba together, and defeated Kaiba, but was defeated by Yami when his Divine Serpent (whose attack power was infinity) was destroyed by the combined form of the three dragon cards (whose power was beyond infinity). He then offered his own soul to the Leviathan, but was released from his influence when the Leviathan was destroyed by Yami. Dartz then returned below the sea with Atlantis, Chris, and Ironheart.