Gabriel is the first character in the comic book series. He is a disillusioned Guardian Angel who “snapped” and rebelled against his “job” of answering prayers and helping humans. He becomes a serial killer, responding to the desperate and suicidal humans. He appears to them with promises to “end their pain” and is charming, soothing, and pretends to be helpful. Then he kills them in gruesome ways, taking out his anger and resentment on humans. His main goal is to “shut humans up” so he does not have to listen and respond to prayers, and he no longer wants to help humans.
Gabriel is resentful of humans because, as a young boy, he was sent to his death during the crusades. When he called out to his Guardian Angel to save him from an approaching medieval army, he was not saved. So he feels that is he was not helped, why should he help humans?
He has the power to control weak human minds. At first, he is not able to touch humans or kill them with his hands, because he is still a Guardian Angel and is forbidden to physically harm people. So, he finds a "loophole": he targets the suicidal, the depressed, and hypnotizes them, making them kill themselves. His murders are not suspected because they are ruled out as suicides.
Gabriel later becomes a Vampire when he is killed by Joseph and as he ascends to Heaven, a vampire hitches a ride and bites him, and Gabriel in turn bites all the angels in Heaven. Gabriel actually relishes this new role, because now he can kill with his own hands and not rely on mind control. He feels like a God, but is more of a criminally insane monster. His rage fuels his serial killing.
Gabriel is a sociopath, with a single goal: to get rid of humans who caused him so much pain and anger and who he hates because he thinks he was forced to cater to them and become their therapists. He feels superior to humans and finds it demeaning to have to help them. He lacks complete empathy, and has a cold, calculating, homicidal nature. He is delusional in that he thinks that he will only be free if he destroys all humans and that this is the only way he can be free of the torment of their prayers. He is manipulative and uses his charms to “comfort” humans and take them trust him before he kills them (and, as a vampire, feeds on them). He is one of the most dangerous of the Vampire Guardian Angels, and also the most impulsive, vindictive, and unstable. He mindlessly destroys anything in his path. His personality is more like that of a ten-year-old throwing an endless tantrums. Deep inside, he is insecure, in emotional pain, and suffering from severe trauma.
The only time he has ever shown regret was when he met Joseph, the stepson of his rival Cameron. Joseph was able to make Gabriel see what he did was wrong and convinced him to go back to Heaven, and killed him in the process. However, after Gabriel resurrects in Heaven and after being bitten by the Vampire, Gabriel becomes even more angry and more vindictive, seeking vengeance against Joseph and Cameron. Although still retaining his charm and manipulative personality, he becomes more of a mindless killing machine in later issues.
Unlike the other Vampire Guardian Angels in the series, Gabriel does not want to be a leader or rule over Vampires and humans. He prefers to just get rid of the whole humankind and anyone who gets in his way.