During the conceptualizing phase of creating the "Legends of Saviors" titles, it was imperative to create the planets not just when the players would visit them, but the entire history of each one, as well. After the effects of the High Dreges' device, many years later, the Low Dreges decided to ban together to pay back what was dealt to them; by eradicating an entire layer of their planet, with all mountains included.
LoS Concept Art | Hatz, Part 3 - Present Phase Time-Lapse