Taking Sarah's body to hell when she attempted to repent on her deathbed within a church in East Bromwich, England, Azzael burned her away so their child would be born, and chopped off the newborn's right hand to replace it with the "Right Hand of Doom", a relic with the power to free the Ogdru Jahad (A destructive, seven headed dragon imprisoned in deep space) and awaken the armies of Hell to wage war against Heaven.

When Hellboy is summoned later in life by Grigori Rasputin, an agent of the Ogdru Jahad, he discovers that the Hand can release and command the imprisoned Dragons of Revelations, and would therefore complete its true purpose to bring about the apocalypse, hence the name "The Right Hand Of Doom."

Hellboy did not always have the Right Hand of Doom, in that he did not waltz out of hell with it upon birth, nor did he moonwalk out of the womb with it attached to his arm. He actually was born with a normal hand -- you know, as normal as a devil baby with a devil hand can be -- and would still have one, if not for his father, Azzazel.