Forgive the lack of preamble but...
What are the limits of this ability and how does it work within the lore? Can any Dunmer summon any ancestor? Sul could summon his own wife. So that seems like it could extend beyond just ancestors. Do Dunmer reach into the Dreamsleeve to summon their ancestors? Do they summon them from somewhere else? How powerful can these spirits be? If you summon a more powerful ancestor will that summoned being be more powerful than another ancestral summon? Is there a time limit on the amount of time you can summon an ancestor before their identity is stripped away in the Dreamsleeve? Can an ancestral summon stay with a Dunmer for a long period of time? Is ancestral summoning racially based or is it actually magicka based and other people could do this?

Basically what is known of this ability and how does it work on a metaphysical level? Reaching into the dreamsleeve seems kind of indicative of a bigger connection between the Dunmer and the Dreamsleeve. Unless of course the summoned ancestors come from somewhere else or it isn't racially restricted.

Thoughts on this? I understand this may not have too much information on it. Theories based on information are welcome.