Terrestrial Liberation Trust (TLT), was formed after aliens called the Visitors warned Earth of the danger of space beasts in 1989. Two years after they arrived Dark Zagi, an evil being created from the Visitors and destroyed their home wolrd, came to Earth after he and his army of space beasts helped him. While on Earth in Colorado, United States he found a suitable human host by the name of Mitsuhiko Ishibori. Thirteen years later he summoned his favorite space beast, The One, to Earth, but Ultraman the Next stopped him. For five years while TLT was creating the division Night Raiders Zagi had Mitsuhiko manipulated to do his dirty work so that the power of Nexus and Next could be strengthened in the Visitor's Lethe, a powerful object that contained Zagi's body. Over the years he would send space beasts, Dark Faust, Dark Mephisto, and the Unknown Hand to be sacrificed so that the power of the Lethe could increase allowing him to regain his body. After the destruction of Ezmael Ren Senjyo, the third dunamist or host of Nexus, died and Nagi Saijyo became the fourth. When he controlled Mitsuhiko for the first time Zagi destroyed a lab that included both of Nagi's parents as a small child which would turn into hatred against space beasts like Zagi planned. After Mitsuhiko revealed he was the controlled of the Unknown Hand and defeated Komon, Captain Wakura, and Shiori with Nagi shortly after. Zagi made it to Sector 0 where the Lethe was and told Night Raiders his entire plan. After Nagi turned into Nexus the Lethe consumed all the energy in her body because of her hatred, allowing Zagi to become himself again. After Zagi returned to his true form he attacked the city of Shinjuku and released all the space beasts in North America with the rest of the world shortly following. After saving Nagi from the Lethe's hold on her Komon became the fifth dunamist of Nexus and transformed as Zagi was destroying the city. Nexus used Anaphas, Junis Red, and Junis Blue as he held his own against Zagi. As the crowd of humans were in awe and had great hope of the silver giant hero winning Nexus turned into Ultraman Noa. As much as Zagi tried Noa easily over powered the fiend and after being literally punched into orbit Noa used the Lightning Noa to destroy Zagi once and for all. While there would still be space beasts roaming the Earth no one lost hope an humanity fought back.
Dark Zagi's statistics
- Height: 50 meters (167 feet)
- Weight: 55,00 tons
- Human Form: Mitisuhiko Ishibori
- Transformation Item: Lethe
- Dark Field G: Zagi can create a special type of dark field known as Dark Field G to do his bidding. He can use it to create a battlefield, transport Space Beast or inhuman form to reflect attacks
- Mind Powers: Zagi has mental abilities of his own, like the visitors who made him, he could erase memories at his leisure as well as use the darkness in people's heart to control them, usualy when they are hosting one of his Dark Giants.
- Lightning Zagi: Zagi can emit an extremely powerful beam of dark energy from his vertical left arm, with his right placed on the back of it. This beam rival's Ultraman Noa's in power, but is still not as strong.
- Zagi Shot: Zagi can emit extremely powerful blast of dark energy from his knuckles. These have an huge amount of force behind them. More than one can be fired at once.
- Gravity Zagi: Zagi can emit an extremely powerful beam of dark energy from his crossed arms. This has a large amount of force behind it.
- Flash Travel: Zagi can incase himself in a large aura of energy to fly to any area he wants.
- Destruction Beam: Zagi can emit a small, yet destructive energy beam from his hands. This can cause large explosions.
- Extraordinary Jumper: Zagi is able to jump to great heights with ease.
- Dark Ultra Powers: As the creator of the Dark giants Faust anf Mephisto, Zagi in theory posses all of their powers
- Space Beasts: These monster, like the dark giants, are Zagi's minions, created via his power and under his total contol.