Sammael was among the original and most powerful of Greater Demons, particularly a fallen angel of the highest order, along with Lucifer and Azazel. He is credited as a responsible party for the beginning of the Incursion.
Sammael was believed to have been created when the world began. He was once an angel, cast away from Heaven and became a Greater Demon, a general of Hell's army. He met Lilith, who eventually became his companion. He was believed to have taken the form of a great Serpent and tempted Adam and Eve in the Garden of Eden.
According to the legend, he and Lilith roamed freely, creating other, lesser demons. They mated with humans and created warlocks, and they were believed to have mated with angels to create faeries. Together, at around AD 1000, the pair performed a very powerful demonic ritual that could be performed only once and never again. The ritual affected Pandemonium and massively strengthened all of demonkind's resistance to the toxicity of the world of humans to them, as well as drastically weakened and thinned parts of the wards protecting the world from the Void, highlighting worn spots and creating holes in them. This allowed large numbers of demons to pour in from tears in the veil all over the world, attempting to devour the life around them. This event became known as the Incursion, the beginning of the period of a large-scale invasion of the world by demons.
This event prompted the eventual creation of the Nephilim. Because of this act, he was hunted down and slain by the archangel Michael with his sword, Glorious. He has not been seen either on Earth or in the Void for nearly a thousand years since, and is widely believed to be dead, or at least destroyed temporarily, only taking centuries to reform in the Void.
In Talmudic lore, Sammael was an important archangel but is also regarded as a powerful demon; he was a figure who was an accuser, seducer, and destroyer, and had been regarded as both good and evil. Rabbinical writings described Samael as the guardian angel of Esau and the Roman empire, and a patron of Edom. He was considered in legends to be a member of the heavenly host, often with grim and destructive duties, and remained one of God's servants even though he condoned the sins of man.
One of Samael's greatest roles in Jewish lore is that of the main archangel of death; sometimes the name of Satan is accorded to him, as well as Death himself, or the Grim Reaper. In Roman Catholicism, Samael is seen as the controversial Angel of Death, the sinister counterpart of the "good" Angel of Death Michael.
Other influence works suggest he was the serpent in the Garden of Eden; he disapproved of the creation of Adam and descended from heaven to seduce Adam and Eve to eat from the forbidden fruit. Furthermore, Cain was born from Eve by intercourse with Sammael.