Engine Gattai Kyouretsu-O is the fourth of the big combining robots from Engine Sentai Go-onger, nicknamed the "Powerful King of Trains." Unlike the Engine-Oh trio, it is formed from the three Ancient Engines that have existed since prehistoric times – and it's exactly that primeval angle that gave the robot its Power Rangers RPM name: the PaleoMax Megazord. Its centerpiece is Engine Kishamoth, a hybrid of a mammoth and a steam locomotive, so primitive that he only "speaks" in mammoth-like roars, which the other Engines and the Go-ongers can nonetheless understand.

Rounding out the team are two bullet-train dinosaurs: Engine Tyrain (T-line), half Shinkansen and half Tyrannosaurus, and Engine Cerain (K-line), half Shinkansen and half Triceratops, who bulldozes through enemy defenses with his horns. In the merge, Kishamoth forms the body and arms while Tyrain becomes the right leg and Cerain the left. Its finisher, the "Kyoretsu Express," first vents a massive burst of KishamoSteam and then brings down a white-hot "Railway Chop" that cuts through even the toughest Banki.

As a DX toy, Kyouretsu-O was released in 2008 by Bandai in Japan as part of the Go-onger line: the large Kishamoth figure plus Tyrain and Cerain, which fold down into the legs. The signature feature is the "Engine Soul" (En-Soul) system – small chip figures slotted into the mecha to trigger lights, sound and voice clips; the DX set includes the Kishamoth Engine Soul, among others. As with the whole Japanese DX line, it carries real heft with die-cast content and elaborate electronics, which is why the Japanese releases are noticeably more screen-accurate than the simpler, electronics-free PaleoMax Megazord that Bandai America put out for RPM.

For collectors, Kyouretsu-O is a cornerstone of the Go-onger system: its three Engines also feed into the ultimate mega-combination Engine-Oh G12, which unites all twelve Engines (the Ultrazord in RPM). Anyone chasing a complete Engine lineup simply can't skip the "King of Trains."