Lethe (レーテ Rēte) was an organic machine created by a species of aliens known as "The Visitors".
Subtitle: Sea of Oblivion (忘却の海 Bōkyaku no Umi)
Pre-Ultraman Nexus (year 1991)
Lethe was a machine created by the a race of jellyfish-like aliens known as "The Visitors". They had created Dark Zagi based on Noa, but the dark giant turned on his creators before he was destroyed. At some point Lethe was created, through unknown means. The Visitors brought Lethe to Earth and agreed to give humans their technology only if they would use it to defend Earth from the Space Beasts. They handed over Lethe and the technology, and Lethe was eventually placed in Level 0 of TLT-J's headquarters.
Zagi, who assimilated a TLT scientist, began an eighteen year plan involving Nagi Saijyo, a future Deunamist. He slaughtered the scientists working at TLT Colorado, America Branch including her parents, leaving deep trauma in the girl.
Ultraman Nexus (year 2009)
After two Deunamists and three dark giants, the light migrated to Nagi's hands and Zagi sprung his trap, leading everyone to Lethe's chamber and revealing the truth about his actions spurring Nagi to transform in rage. This caused Lethe to trap Nagi, having sensed her rage and the fear behind it being connected to one of its keywords for memory erasure. Due to Nagi being in Ultra form, this meant the construct would drain her light and convert it into a dark power which Zagi used to restore his old body. The construct was destroyed when Kazuki Komon freed Nagi from the darkness, the two merging with Ultraman to revive his light.
- Lethe's Energy Core is said to be due to it being made from the remains of Dark Zagi's original body.
- This claim that is highly dubious as official documentation has Zagi's body being destroyed by Noa's Noa The Final technique. It is possible that Lethe was created using similar means to what the Visitor's used to create Zagi.
- The prop of Lethe was actually made by recycling and modifying Alien Monera's spaceship, Monera Seed.
- Length: Unknown, taller than Nexus
- Weight: Unknown
- Origin: The Visitors' planet
- Powers and Weapons
- Visitor/TLT's Usage
- Flight: Lethe can easily levitate atop the sky.
- Memory Seal: Lethe can seal memories, such as the ones from Space Beast witnesses and even entries in computers.
- Zagi's Usage
- Shadow Tendrils: Lethe can make tendrils of darkness from its body.
- Energy Absorb: Lethe can absorb energy based on hate and anger and convert it into a dark energy.
- Transformation item: Once gathering enough energy, Lethe can restore/transform Zagi into his original form.