Richard is never seen directly but is mentoned by Alex, Deleo and Morden in the book along with his mansion being seen in the dreaming when Alex is trying to contact Luna. What is known is that Alex's group of apprentices was not his first and he has been tormenting and testing them to make dark mages for years and at some point tortured Alex.
Alex Verus: Known to lock Alex up and torture him or get one of his other Appretices do it for him with a bit of luck and his diviner powers he was able to escape and has not seen Richard since.
Deleo: Rachel as she was known back then endured her torment over time becoming a cold woman who now wears and mask as the Dark Mage Deleo.
Shireen:A redheaded young woman who was killed while under her apprenticeship. she is seen in the first book as a resident of the dreaming when Alex enters it to warn Luna acording to their talk she tried to steer Deleo back to the Light but failed.
Tobruk: Richards top student Toburk used to free Alex around the mansion and hunt him down in a game he called cat and mouse at some point Alex killed him. He is seen as a resident of the dreaming in Richards mansion and at one point turns into a flaming skeleton while Alex is talking with him.