This article contains plot details from the latest book.
Ancients are essentially the oldest elves that live. Since no elves have died of old age yet, the Ancients are some of the oldest living things on the planet. They usually have pointed ears as a sign of maturity/age, first stated in the first book. They rarely accept visitors and typically live in solitude, because they've amassed so much more wisdom than others that it's hard to relate to people.
Vespera: She was alive when humans still lived in Atlantis, and Fallon was a Councillor. She has a history of being a prisoner in Lumenaria, washed out of the councillor's minds, and generally causing havoc for Sophie and her friends to fix.