Angels are designed to be the bringers of Light from the spiritual realms to the physical realms. They are messengers of God. They are Feeling Beings. For example, they are Love, Purity, Joy, Faith etc.
Angels are indeed not ET's.
As it says in Revelations, Michael and his legions banished the fallen angels from the spiritual realm, so many of these fallen angels did indeed take on physical bodies. However, non-fallen angels are Beings of Light that are meant to be the connection between the Spiritual realms and the physical realms. We are a team.
It's important to understand that the 4,5, and 6 are all physical dimensions like the one we are in, (only vibrating differently). Angels move between the higher spiritual realms (Above true 6th) and the co-creators in the lower dimensions (including the et's that are in the 4,5 and 6 ~ Description of dimensions is here:
http://projectavalon.net/forum/showthread.php?t=16911 )
Here, if you would like to see some good representations of Angels you can take a look at some of very inspired images here:
http://www.mariusfineart.com/Gallery1.html
And consider spending some time connecting with these images and the Beings they are of and 'feeling' for yourself.
At this point, I'm almost (but not quite) a little disappointed I actually mentioned James as being a wonderful source of info, because again, while I respect James very much for speaking out, I disagree with most of his interpretations of the big picture in these documents, however, I find his personal experiences as a child soldier and stuff like that to be very interesting and worthwhile reading. ~~~
I believe the reality is that the galaxy itself is a fallen place (but the whole thing is about to rise higher and it is definitely not fallen everywhere but a lot of it has been), and walk-ins will be taking with them whatever ET beliefs they had when they were up there. They were not Christ Beings up there, and they are not Christ Beings down here (yet), so we all have our own illusions to work through. Spiritual Truth is higher than ET's, why people are afraid to look beyond the ET's I can only surmise is the matrix at work personally.
We're all in this together now, and it's up to each one of us, walk in or not, to come up higher in Truth

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I also don't know that his walk in story is mentioned in these materials, it was elsewhere I believe.