Reality Levels

Reality can mean a lot of things, but in this context it is a fundamental property of a space or an object. 
Reality is a complex and esoteric facet of natural law, and explaining the math and frameworks involved is beyond the scope of this text. However, reality levels are an important part of understanding Valan magic and phenomena, so some level of context is necessary.
In a nutshell, reality is a natural property, much like mass, charge, alignment, and all others taught in any natural philosophy class worth it's salt. Many make the mistake of equating reality to ethereality, but they are fundamentally different. A common example used for ethereality is the difference between unformed clay, volatile and unformed (which representing high ethereality), and a sturdy clay pot, fully formed and largely immutable (representing low ethereality). A similar comparison for reality would be the difference between a character in a book, a portrait, and a person standing in front of you, representing low to high reality, respectively. A person is complex and has great power and influence, and cannot be easily altered without strong magic. A portrait is not alive and is not as complex, and can be altered with the right skill and vision. However, it's complex and real enough that some magic might bring it to life. Finally, a character in a book is not very complex, far from alive, and can be easily altered by scribbling out what you don't like and writing in your own notes.
Valus is slightly less real than other worlds, meaning it's more variable, and things with naturally high reality values, like souls, can more easily alter it. It’s inhabitants are only slightly less real than outsiders, which explains why magic and other powers have more effect and influence in this sphere.

Reality in Depth

This is absolutely not my field of study. I am a world lore and history professor, not a metaphysics professor. So, if this info is misleading, take your complaints elsewhere.
Reality is a measure of how real something is. It measures how stable information and detail is as it gets smaller, and how easily it changes. With very low reality, an object might exist one moment and disappear the next, or change color every time you look at it. You may even be able to change it with your own will and perspective, especially if you have latent psionic potential. In a naturally low reality world, objects wouldn't likely be able to interact consistently for long enough to form bonds, much less create life. With very high reality, an object might impart it's own reality and rules onto you, and appear overwhelming and incomprehensible to the senses. Most magical creatures, spirits, and especially deities have a higher reality value with which to enforce their perspective of reality. In a high reality world, there would be so many rules and hard lines, ironically life could likely never form as we understand it there either.
A disturbing conclusion we can draw from this is that life can only exist within a narrow band of reality values. We are very lucky most realms fall into this band, or life would be much less prevalent in the universe.

Type

Natural