What density are angels?

[Infinite]

Angels are not from a density.  They are non-evolving beings created by the Logos to maintain various aspects of Creation.

Second Q'uo, there are angels which never incarnated, but there are also angels which evolve through densities:

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The hierarchy of the angels of which you have asked us is just as regular and predictable. You have angels at the level of Creator, and you have angels at the level of personal angels. You have everything in between. They carry responsibilities according to their hierarchy. What makes angels unique is that they have never left the vibration of the Creator. They have never departed from the one original Thought of unconditional love. They have never incarnated and they never will. While they have characteristics that can seem to be like a personality, to say that angels have a personality is to anthropomorphize [1] incorrectly.

Angels are love. Angels are love responsible for realms in a hierarchical manner. There are those which work with your sub-Logos, the sun, in creating the archetypal mind and the blueprint for the densities in this particular creation. There are angels who are attracted to vibrations and flock to those whose vibration are beautiful to them. You may not feel beautiful, dear ones, especially when you are struggling, yet to those who vibrate in unconditional love, the qualities of one who is seeking to learn and to serve are irresistible. It takes a great deal of courage to persist in a spiritual preoccupation, and each of you is [very] beautiful to us and to the angels.

There are two basic energies which angels have to offer. One is the simple energy of love itself and the other is a feeling of safety, which could be called a healing energy. Both of those aspects are the resources which angels have to offer. Angels also have connections with the four elements and the four directions [2] so that as you become more and more aware of the correspondences between certain archangels and certain energies, certain powers and certain directions, you become more able to cleanse your habitation or the area around you with the help of the archangels.

There is another class of angels that is indeed angelic and yet [these angels] have had incarnations. Those are the entities who have chosen to be angels but were not angels from the Creator. Yet between incarnations it became apparent to these souls that the work that they wished to do was angelic. And so these entities were incarnated and lived for a short time on this terrestrial ball you call Earth. And then, seemingly far before their time, they were taken. Instead of moving into the healing of the incarnation and the choosing of another incarnation, these particular entities move into the angelic realm. They are able to become angels because of their innocence within incarnation. These little ones are especially fond of those whose hearts are open and are very grateful to rest in that open heart that will accept them.

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Source: http://www.llresearch.org/transcripts/is..._0212.aspx