The process can go wrong sometimes for me. I have written as much as forty pages with a character and then decided I was in a fog or a dead end. I've thrown out the material and begun again. But most of the time, character is somewhat spontaneous. In my cosmology, Tiffany, vampires who starve become progressively weaker until they reach a point where they can not help themselves.
Older vampires can endure longer without feeding, but they are like addicts.
They want to feed. I'm not sure that Lestat was duped. I deliberately left the novel with the mystery in tact. Possibly Memnoch told the truth and Lestat could not accept it. Possibly Memnoch used Lestat to derail the new religion being started by Dora, the heroine of the novel, but possibly nothing like that was accomplished.