Sauron

Sauron is a supportive character in the Valinorian Chronicles and is briefly introduced already in the first book (Freedom). He is the main antagonist in the Resurrection of Sauron-quartet and The Time Before, and a more supportive antagonist in War of Magic. He was the Dark Lord of Mordor and the creator of the One Ring.

Spoilers

 * In the Valinorian Chronicles Sauron has been given a smaller role in the Freedom Trilogy due to that the writer felt it was more important to introduce the reader to the Moriquendi and to Saruman, who feature more in later books