Yes, much of this has been asked before. Here is my memory:
Polaris mentions that there are beings incarnate on this planet and/or plane that do not exist within physical bodies. I wonder if there could be some elaboration on that statement.
If you can think of "levels" of the physical plane, it's like that. There are beings that are at a different vibrational rate of matter. They exist just the same and are definitely on the physical plane, but don't exist on the same wavelength as us.
After we visited New Zealand, we were curious as to how the native Maori got there. The response was actually along these lines - that for a long time, a certain culture of humans due to their consciousness were existing in a different vibration. This made them invisible to most of the rest of humanity. After thousands of years, they made a collective choice to join what we know of. [My skeptic attitude raised its eyebrows, but actually this is similar to some other Seth ideas]
I am aware of the entities that make up Polaris (Micheal, Seth, etc.) I would like to know if there are other entities that exist within the same (causal?) plane as Polaris and if so do they have a role in teaching or guidance?
Essentially an infinite number. Just think how many life forms exist on the physical plane that we know of, let alone those we can't comprehend. Even if you divide that by 1000 (for an entity recombining), it's still essentially infinite. And they're all involved in teaching in some way. But that could be said for just about every being - including you and me.
Expanding further from that, are there entities that exist within the ‘higher’ planes of existence? And if so what is their experience and interaction with beings the ‘lower’ planes?
Every time we've asked Polaris about their direct experience, they try to say some things but also say how difficult it is to convey a real experience into something as mundane as words. Usually Karen gets quite a high when they try to show her something directly, though.
Lastly I wonder if you could shed any light on the entity that is ‘Abraham’ of the Abraham Hicks fame. I would like to know if they are a causal plane entity and what if any is there involvement with Polaris and if they exist in the same context or form.
Karen channeled Abraham as a lower level causal entity about 6 months ago, and called them friends.
Hope that helps! There has been a lot of channeling not posted here for whatever reason.
