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.
The 3rd and more dire Phase out of all of the planets within the Sero Perspective, Signa's inevitable and irreversible transformation into something much farther than it ever was, takes hold and almost doesn't let go up until the last, and final Preservation Sanctuary in the southern pole.
LoS Concept Art | Signa, Part 3 - Present Phase Time-Lapse