The Arc-Gurren (アークグレン, Aku-Guren?), named by Rossiu Adai, is one of Lordgenome's Gunmen battleships, a Dai-Gun, which his armies used when he was a Spiral Warrior during events prior to the series. It is enormous in size and comparable to the Dekabutsu. It is initially used to gather hundreds of thousands of animals and people onto it to escape world-destroying events later in the series. It uses Spiral Power to run and only recognizes Lordgenome as its operator. It is capable of going into space for at least a year, and contains an array of large-scale defensive systems and weaponry.
Before Anti-Spiral War Arc
Before the war with the Anti-Spirals is under way, the new government finds Arc-Gurren buried below Parliament Tower, and formulates a plan to use it as a method to escape the impending collision of Earth's moon with Earth's surface. Rossiu issues orders for as many animals and people to be loaded onto the ship as possible, and expects Arc-Gurren to hold out for one year orbiting Earth as its surface cools after the impact.
The new government is forced to rush their plans when Arc-Gurren is activated with the use of Lordgenome's head as its biocomputer, causing swarms of Mugann to begin attacking Parliament Tower to reach it. The Arc-Gurren is eventually forced into space in order to escape the attacking Mugann, however is only met by more Anti-Spiral forces from and surrounding the moon. As the Mugann close in, the people's confidence in Arc-Gurren begins to ebb, and its spiral power decreases, making it more vulnerable to the Mugann's attacks despite protection efforts from a legion Grapearl units.
Simon and the rest of Team Dai-Gurren appear, however, and fight back against the Mugann onslaught. When Arc-Gurren is cornered by two large Mugann, Leeron tells Simon to combine it with Gurren-Lagann, which causes Team Dai-Gurren to form Arc-Gurren Lagann. The resulting combination is able to knock out the two Mugann, who combine as well, and create a hole in the space time continuum.
After the battle, the Arc-Gurren Lagann was used to hold back the moon as it tried to crash into earth ahead of schedule, and when it was unable to push it back, Gimmy Adai and Darry Adai took its controls using their Grapearls while Simon used Gurren-Lagann to take back the moon. In the movie adaption, Arc-Gurren Lagann instead breaks the hand of the Cathedral Lazengann with its own Giga Drill Break and the mech itself pushes its Giga Drill into the moon's core.
During Anti-Spiral War Arc
The Arc-Gurren, in the form of Arc-Gurren Lagann, is only seen outside of the Cathedral Terra when Team Dai-Gurren first enters the Anti-Spirals' pocket-universe. Once it becomes the Ultra Spiral Powerplant that powers Super Galaxy Gurren Lagann, it is only seen acting as such within the mech until the end of the series. In the movie adaption, it is only seen acting as an Ultra Spiral Powerplant as well, and again only until the end of the series.
- Arc-Gurren's mech form is the only Gurren Lagann stage (besides Lagann itself) to lack sunglasses on either face.
- When plans are being made to evacuate the surface of Earth, the screen showing the evacuation data spells the dai-gun's name as "Ark Gurren". This may be a reference to Noahs' Ark, which was also created and used in the face of great disaster.