Found: Dohati's Castle
MP Required: N/A
After destroying Dohati's Mist Generator, an unknown Ra-Seru is discovered and witnessed from all the heroes. The Ra-Seru are all speaking an unknown language, which Noa asks Terra about. Terra responds that they will explain what happens later.
Later in the game, it's revealed that all Mist Generators are created using the Ra-Seru. In the process, the Ra-Seru are then "controlled" to create the Mist and to work for it. The Ra-Seru had feared that telling the heroes about what they were doing would frighten them of the Ra-Seru and think of them as their enemies, which of course does not happen.
I don't know about anyone else, but isn't this one an awesome looking Ra-Seru? Too bad it couldn't have been obtained!!