Brandon Sanderson
I intentionally left seons--their origin, their connection to AonDor--a little vague in ELANTRIS. The reason for this is that I intend the secrets of the Seons to be a major plot element in a sequel to the book.
I didn't want to put very much about them in because I knew that it would be years before I got to do an ELANTRIS sequel, and I wanted to give myself enough 'wiggle room' to not confine the second book, which isn't fully formed in my head yet. Anything I say now could ruin the plot for people before I even write the book--or, it could end up being untrue, as I develop my ideas further.
Eagle Prince
Can they go through walls? Are they incorporeal like a ghost? I'm guessing they can't move stuff around, because Ashe says something about the Elantrians wanting him to bring them food but he couldn't. And then when Serene was on the wall, he just shouted at her, like he couldn't just knock her back or anything. But then several times it talked about them going through windows, and some of the Elantrian seons bouncing around like drunks.
Brandon Sanderson
Good question, EP.
I answer this in the text just briefly, but it doesn't come up a whole lot. At one point, Raoden's mad Seon tries to float through a wall, and he bounces off of it. I wished to imply that they did have substance, but they were very light, and therefore unable to exert any great amounts of force.