Around 5 years ago I was teaching forensic classes for the FBI before I was brought back into the field to work alongside Hannibal Lecter profiling criminals. It was my ability to get into the minds of serial killers that caught Jack Crawford's attention and this ability has caused me many problems in the past so Jack assigned Hannibal to be my psychiatrist while I worked in the field. 
While under Hannibal's care I was manipulated, gaslit and framed for multiple murders.

Former professor and criminal profiler 

My form of therapy is to be a place where anything can be said, and then to find ways to explore that darkness instead of simply rejecting it. I see myself as the only one, apart from perhaps Will Graham, to see the true nature of God, and follow this nature. I can see the beauty and power of taking a life, and I am drawn to it. By the consuming of the victim, I can further humiliate them in death. It is not cannibalism, because my victim will never be equal to me. 

A dedicated psychiatrist.

In the beginning, I was a "wily old serpent" in the Garden of Eden where I met the Aziraphale, who I then happened to bump into around once every centaury. I was assigned to Earth to "make some trouble" which isn't nearly as hard as it sounds, because the humans tend to think up things far worse than I could ever imagine. After some time, the angel and I started a sort of "arrangement", so every now and then I might pop in quick blessing in between temptations, to save him the trouble. 

Fallen angel who just hung around the wrong people

I am looking to prevent the apocalypse because I enjoy humans and I likes my life on Earth. There are restaurants on here, for a start. Furthermore, I do not find the idea of listening to The Sound of Music for eternity very appealing. I am friends with the demon Crowley and we have both been on Earth since it's creation, 6000 years ago. Despite being my hereditary enemy, I quickly grew fond of him and believe that deep down, he is a good person.

Angel and book shop owner

The demon Crawley in the year 2500BC. Known as Bildad the Shuhite, the good friend of Job and Sitis. Master of Shoemaking and obstetrics.