When someone is sleeping what planes of existence do they visit according to the Great Wheel cosmology in D&D 5e?
I have not found exact information in the rule books about this. Perhaps there are options (good dreams on one plane, nightmares on the other)?
As far as I remember, in one of the previous editions there was a separate plane you went to while dreaming, but what about for D&D 5e?
Is there a mechanic, for example, describing a transition during sleep, a possible death during sleep, or a transition to another person’s sleep that would shed light on this issue?
Maybe there is information compatible with D&D 5th edition in the books about Planescape (since we are dealing with the Great Wheel)?
Please provide references to the sources.