Astral beings are Others than are certain things made manifest, such as dreams, nightmares, and curses. They appear to be similar to Wraiths but lack the weakness found in them and require preparation in advance to deal with them effectively.
The one initally showed in the story was narrow, tall, naked and simultaneously sexless, with only dark pubes at the nether regions. Its flesh was mottled like that of a corpse, or maybe a baby fresh from childbirth, it had spidery fingers that each had two or three joints too many. It moved like it floated, leaving no tracks behind it, legs only periodically moving to propel it forward. The front of its head looked exactly like the back of its head did. A tangle of hair, blowing in wind that wasn’t there.
Astral beings are incredibly difficult to deal with unless an spirit-entity interacts with it or counter-measures were prepared ahead of time, such as dreamweavers. It can interact with solid things but the same things could not touch it, leaving it to be a one-sided affair in a conflict. Crone Mara uses one for a guardian for her woodlands for this reason.