Unknown Physiology: Myst is a being of hardened cosmic gas, lacking any sort if internal structure. He is not truly solid, and can be pushed through with enough force, or cut by sharp objects. If cut, his essence will leak, causing his size to shrink and allowing him to be trapped, requiring him to sleep to recover.
Being made of gas, Myst is naturally buoyant, floating just off the ground naturally. He does not walk, instead flying everywhere, and are capable of reaching 60 mph. He cannot submerge himself in water without bobbing to the surface, and any more than a light breeze can blow them away.
Myst's body is ever-changing, capable of taking any shape between 1' and 12' in size. These changes are purely cosmetic: no matter how Myst changes himself, he always has the same general look. His voice is glitched and sounds as if it is coming from multiple places at once. His body also matches his mood: when happy, the stars on his body will shine brightly enough to light up a small room.
Myst's senses are significantly difference from that of a human. While he has excellent hearing, on the level of a predator, and night vision, he has no sense of taste, smell, or touch, except when in a dream world.