In the fourth trilogy, known as Vampire Destiny, Darren is forced to make some difficult decisions, finally taking his destiny into his own hands and dealing with the consequences.
In the tenth book, The Lake of Souls, Darren travels to an unfamiliar land to find out who his best friend, Harkat Mulds, used to be; as a "Little Person", Harkat's mind sans memories was placed into a new body after his death.