Cosmology: Kythri, the Akashic Record
One of the nine planes that forms the junction between the planar universe of Trinity and the beams on which it rests, Kythri - also known as the Akashic Record - was formed from the intersection of Trinity and the Blue beam.
Kythri rests at the intersection of Trinity and one of its supporting beams, specifically that of the Blue, a stabilizing force of memory and causality.
Though many memeticists refer to the Blue as the akashic record, that does not mean they are referencing Kythri specifically. Kythri is not the world memory itself, but is instead a physical manifestation of it - essentially a library that contains all of the world's knowledge, ever expanding as that knowledge increases, recording history and knowledge. While one can interact with the world memory both in Trinity's prime and Kythri, it does not exist in either of those locations: it is a function of the Blue beam and its interaction with Trinity.
Kythri has no one true appearance. While individuals who travel to it speak of the same layout, what they actually see differs wildly. One individual may see ancient stones and racks of papyrus scrolls; another may see stack upon stack of digital media storage; while yet another may see the entire plane as literal data, streaming everywhere and compressed into "physical" formats to form what they sense as walls and other physical aspects of the plane. Kythri's representation to one individual is dependent upon their understanding of how knowledge is stored, and what - in Trinity - it represents. Omnipresent across all of its manifestations, however, are mirrors: many surfaces throughout the plane are mirrored, or have mirrors mounted upon them, in a wide variety of fashions related to the plane's manifestation for a given individual.
Regardless of how it is perceived, Kythri is very much akin to a vast, unknowable library: some sections have high-vaulted ceilings, with ample space for desks and chairs for those who seek to study the world memory directly; while others are cramped, full of ancient and seemingly-lost knowledge, untouched by the ages. The precise architecture and layout of Kythri responds, in some ways, to how the world memory itself is accessed: more recent, accessible knowledge is found in the open, well-lit sections, while knowledge lost to mortals lies behind gates and doors, locked by forces beyond mortal ken - inaccessible from Trinity, but tantalizingly close within this realm of pure knowledge.
As with all Force-aligned planes in Trinity's cosmology, the entirety of Kythri has a subtle hue to it: literally everything on the plane has at least a hint of blue hue to it. Those creatures who visit find themselves, and their possessions, taking on the same affectation, even after minimal exposure to the plane.
Summary: Envision Ravnica, but instead of a city, it's a library, with the specific aesthetics filled in by an individual's mind and how they think about information storage.
As with each of the nine planes created through Trinity's interaction with the beams, Kythri is home to a variety of Blue-aligned elementals. Mementals, in particular, are rife throughout Kythri, often spontaneously spawning and disappearing with seemingly little reason, though here they are intrinsically tied to the plane and are natural extensions of it, as well as being physical manifestations of the Blue. In addition, there are a number of spoken who have traveled to Kythri and decided to remain, and can be found throughout the plane - though few are interested in interacting with others, with most obsessively researching some topic or other dear to them.
Similarly, being so much closer to the source of their hunger, vilekin attuned to the Blue can also be found in Kythri - though unlike in Trinity, they are often significantly more docile and more likely to remain dormant. However, in the darker and quieter stacks, it is possible to come across a voracious and territorial vilekin that is not easily appeased.
The most numerous occupants of Kythri, however, are the occuria, who claim this plane as their home and demesnes.