Infraspace and the home of h'Karn, a species who's existence relies a lot on our own
As 'light' from the source radiates outwards, mundane creatures block some of this energy and creates a three dimensional shadow down in the planes where rules are less strict. They have the same personality as their upper companion (anchor) even if the lives they live are very different.

Glass forest are a vast old-story forest of geometric crystal- as light refracts through it, each prism'd beam splits out and zips around for who knows how long, a glittering rainbow of all different colors glinting from every angle.

(ref coming soon)
When a h'karian inevitably outlives their anchor, they experience ego death and must go on a lengthy journey to build themselves back, the consequences of failing to do so can lead to uncontrollable anger, grotesque transformation, and eventual death via Sentinel intervention.
h'Karn without an anchor who have found this completion of self live indefinitely unless harmed. Followup personalities often take notes from their previous, but almost always diverge in very drastic ways.

Additionally, these funny shadow birds often have a psuedo-religious relationship with the 'anchor whos shadow cast made them', regarding these anchors in some way as their deliberate creators.