"The Wheel of Fate must turn; all are redeemed in the cleansing agony of birth, death, and rebirth. This is the Engine of Life, the purifying rhythm of the universe, to which all souls are irresistibly drawn."
The Wheel of Fate is a prominent plot element throughout the series. It is an inexorable cycle of birth, death, and reincarnation to which all living creatures in Nosgoth are compelled. The Wheel describes the paths that one will follow in life, and will compel them to follow it. As such, no one in Nosgoth truly possesses free will.
Raziel's resurrection as a Wraith ostensibly rendered him exempt from the Wheel, granting him true control over his destiny. Additionally, as vampires are immortal, their souls do not spin with the Wheel, though this does not mean they have free will.