|This article is about a/an lair in Engine Sentai Go-Onger.|
Hellgaille Palace (ヘルガイユ宮殿 Herugaiyu Kyūten) is the base where the Barbaric Machine Clan Gaiark are located. It is located on an unknown island in the Pacific Ocean. The palace in itself takes the appearance of a mass of moving machinery and smokestacks spewing dark air pollution into the skies; with most of the main locations within the palace being underground. The main center of the palace is a meeting room where the Pollution Ministers and other Gaiark executives tend to plot and scheme; the room includes a machine for the creation of Banki Beasts and a bar where the Pollution ministers tend to get drunk on oil after particularly bad defeats against the Go-Onger or the Engine. However it's central element is a special giant gear known as the "Deus Haguru Magear", which is used by the squadron to create energy for the manufacturing of Bandohma fighters used for combat. Unknown to the main Gaiark leaders outside Land Pollution Minister Yogostein, the gear can be activated to a point of building an unlimited number of Bandohma, allowing for an army to be created non-stop to lay entire Braneworld dimensions to waste. The hanger where the Bandohma are stored is another notable area within the palace.
The location of Hellgaille Palace was unknown to the Go-Onger for most of the season, despite potentially having the means to discover where it was at the cost of exhausting Bomper due to how much energy would have been required for the Go-Onger to find it. Prior to the final battle, Land Pollution Vice-Minister Hiramechimedes nearly revealed where it was to Go-On Gold during a ploy to fake defection in order to destroy the team on another island in the ocean.
Ultimately, the team decides to find the island after nearly their entire team is eliminated and sent to a dimensional void by Crime Minister Yogoshimacritein as he released the full potential of the Deus Haguru Magear. Sosuke, Renn and Saki infiltrate the island using Engine-O and ultimately destroy the gear, but Yogoshimacritein decides to use his power to reverse the machinery after it's destruction as a last-ditch effort to eliminate the Go-Onger trio and to grant himself ultimate power from whatever stores remained within the palace. It ultimately collapses into the ocean with the Go-Onger escaping and the Crime Minster ascending to near-godhood prior to his ultimate defeat by the entire seven-man team.
- Hellgaille Palace's name is a portmanteau of "hell" and "Versailles"