
Originally Posted by
Spira
There's no actual lore for Limbus.
However, you can draw inferences from the CoP story to figure out how it happened.
Apollyon is actually Lower Promyvion, or Promyvion-Al'Taieu, so it isn't very much different from the other Promyvions, except that it wasn't caused (mainly) by Selh'teus drawing light from the ark but by the crystal naturally losing power due to power drawn from the Crystal Line and possibly in relation to Promathia himself. It's like a distortion in space created by the absence of the crystals light.
Temenos, on the other hand, is actually Ou'Phat's Obelisk, which iirc is less of a lab and more of a mausoleum. The existence of beastmen and weird creature is actually anomalous, but it likely has something to do with a distortion of the crystal line as mentioned by Ophannus, which all things supposedly return to in death - explaining the presense of Doggdvegg.
therefore, not Odin, for once