This information is still a work in progress, so it may be rough.

Let me tell you a story about the creatures in the sky.

 

There are dark forms- no, they are not dark...some of them are only spread across the entire sky, their arms are so far that the eye cannot see the end... Others are young and quite small, their galaxies are still young. 

 

The Astral Walker,as a being, is a very rare creature. The lore states that they are created when stars are formed, a surprise creation out of the process stellar nurseries take when they collapse and form stars. While creation of stars is relatively common, the formation of an Astral Walker only happens by a one in a million chance.

These creatures are born with a galaxy at their center, which start out small and, as they age, they lose ability to hold gravity and slowly split. An astral walker is powered by the life force of what lives within it, feeding off of the life and death, whether that be exploding and creation of stars, or the death and lives of creatures that live within the tiny stellar world. 

So there are not many of them compared to the size of existence itself, and they are spread across all of space and time. If an astral walker dies, with their passing they leave behind stars, and more life than they held when they were living. 

Sylenvie will live an insurmountable amount of time, which would be difficult for any race to measure. By the time she disappears, most species that began in her will have disappeared. 

They have the ability to condense and expand to a certain limit without effecting anything besides their own boundaries, but as an Astral Walker gets smaller their eyes become brighter, they glow brighter.... So in essence, if they were the size of a person, they would blind them and burn them..incinerate in fact, if they do not let part of their bodies go. 

The theory of those who know about the Astral Walker, or have the inkling of their existence, is that if you see a comet in the sky, it's often one of them traveling out across space and time, looking at the stray solar systems within basic galaxies.