Dark Zagi is one of Ultraman Nexus's enemy. He appeared in episode 7 & 12.
A year before the event of the Nexus series, Riko Saido met Komon Kazuki at the Zoo and the two hit it of. That night Riko drove home with her family, her mother, father and brother, only to be attacked by the Space Beast Nosferu. The beast disabled there car and thought she escaped her family was killed when the car exploded from the monster's attack. Distraught with anguish, suddenly a Night Raider appeared and aimed his weapons, Mizirogi Shinya, who then turned his weapon to the unsuspecting girl and fired straight into her face. After that she was revived by Mephisto's dark power, but not as a Beast Human puppet, instead she was a suitable vessel for his servant the lesser Dark Giant Known as Faust. Since then Riko and Komon started a relationship all the while the lived in a dellusion forced upon her, wherein her family was alive and well.
In modern time, the light of Noa found it second vessel, Himya Jun. As Jun was about to turn into Nexus because of Bugbuzan's reappearence Faust appeared and started to use dark energy bolts to attack him. Faust claimed he was Jun's shadow and the human soon turned into Ultraman Nexus. After going into Junis Red Nexus created the meta field Faust over powered it with the dark field. In the land of darkness the two clashed and seemed to be evenly matched until Faust used the dark cluster, causing a volley of dark energy balls to rain down on Nexus. Just as the hero got up his color timer began to blink and Faust began to over power him. However, Nexus didn't give up and after using the Cross Impulse Faust retreated with the dark field, vowing to soon return. True to his word, Faust returned, as Jun was investigating Lafleya's latest three victims, wanting the human to turn into Nexus, a attacked eventually forcing the human to face his fear of the dark field. The two giants soon fought, but once Night Raiders appeared, Faust vanished. As Nexus fought Lafleya in the meta field where Faust appeared from underground and used the dark field once again. The combined effort of Lafleya and Faust seemed too be too much, but after some clever usage of the Phase feather attack, Faust soon retreated as did Lafleya. However, one of the Phase Feathers deflected by Faust hit the Night Raiders' chester knocking outof the sky. That morning Komon woke up with Nagi missing from her seat. As he went to investigate he found his girlfriend, Riko, unconcious holding Nagi's dogtag. Upon Nagi's appearance she tried interrogating her, even throwing Komon out of the way but the frightened woman had no asnwers for her. That night Lafleya and Nexus fought once again with Faust returning, but after the Night Raiders used the Strike Vanisher to blow the space beast up Faust was heavily damaged and was forced to retreat. Around this time Riko started having visions and hearing voices, she was being tormented by Faust and his master Mizorogi, who erased her memories to turn into a true puppet. Faust showed up once again after Riko went missing and Komon encountered the fiend, blocking his path on the road. After saying Riko dissimissing Riko he was about to kill Komon, but Jun showed up just in time and fought the fiend as Nexus. The two fought once again, but this time Faust didn't use the dark field and was soon pumbled. After retreating Faust was going to fight his final battle with Nexus. Komon and Jun both found Riko in the forest, but now only Faust was incontrol and revaled the devastating truth to Komon before transforming. The two giants met once again and clashed in Faust's dark field once again with Komon somehow sucked inside. By standing over Komon, Faust used him as a hostage to pummel Nexus. With the hero down Faust latched on to ready to drain him dry. As Faust began to drain Nexus's energy Komon fired a shot at Faust, reviving the sealed memories of Riko to the astonishment of Faust's watching master. Because Riko now possessed Faust, the dark giant's person was dead, Mephisto summoned Nosferu to kill Komon, but Riko sacrificed Faust's body now her own, giving her life for her beloved. After Nexus blew Nosferu to pieces with the Cross-Ray Storm Komon was by Riko's side until she died, in his arms she disappeared into particles of light, leaving behind a devastated Komon to battle with a serious depression. Even though Faust was now dead, there would be worse agents of darkness than him to conquer the Earth, such as his master, who would now target Komon