His name means "Blindness of God." Clearly he occupies the role of the principle of evil, opposed by Michael, the principle of good. He was the angel which wrestled with Jacob and then named him Israel. He tried to persuade Abraham not to offer his son for sacrifice. He and his cohorts were the angels who raped women early in the Genesis account, and gave birth to half-breeds, the nephilim. Contradictory accounts attribute Cain being either from a union of Samael seducing Eve, or Adam having an affair with Lilith. Through Cain contributing to the gene pool of humanity, the ability to do evil was now available to them. Thus either Lilith or Samael are responsible for the ability to sin among the third kingdom, mankind.
In Darksiders he continues his role as prince of demons. However, he rejected the Destroyer's rule in Hell and was sentenced to eternal imprisonment. In the game, War frees Samael and makes a pact with him: War must bring him the hearts of the Chosen in return for Samael's assistance in helping War regain his former powers. Samael's wings are turned upside down as a crude reference to the angels he betrayed. Australian actor Vernon Wells lends his voice to the menacing demon.
Once Samael has all four Hearts of the Chosen he is shown with orange power pulsing around him as his original powers are restored. He then threatens War by saying that he could kill him, but he steps back and explains that he will not kill War because he (Samael) has a code by which he does business. Besides, he recognizes a "Quest for Revenge" when he sees one, and revenge he respects. Then he creates a portal for War to travel through. The Watcher tells War not to enter the Serpent Hole and that it may lead to Hell. War ignores him and continues through the portal, which leads him to The Black Throne. Samael says "We will meet again." as he watches War and the Watcher enter the portal to the black throne. He does not appear in the game again afterwards.
It is unknown how powerful Samael is, but he is definitely a strong dark force to be reckoned with. Even though he is imprisoned, he appears to give War several different powers, such as Shadowflight, and Chronomancer. He is also able to see War's every action from a distance, thus he appears to have some level of omniscience. When his powers were restored, he boasted he was like unto a god.
Intriguingly, Samael displays various vampiric traits. His prison encompassed a blood related mechanism, whereby gathered blood was sent to him to free him. It was through drinking the blood from the hearts of the chosen that he was able to regain his former powers. Every time he displays use of his powers, particularly when teleporting, flying or opening portals, bats are seen hovering the area of effect. It is also pointed out that Samael's power is great enough to take on all four of the horsemen as he said to war when they first meet up in the campaign "War come to play executioner...... they should have sent all four of you"