Satan

Satan is a leader of Hell.

Background
Satan doesn't give second chances, and neither do his playmates.

There is nothing new about Satan... He's been around since before biblical times. Why, you can't go to church without hearing about the Prince of Darkness.

After escaping Deimos, the Marine is transported to the surface of Hell itself, where he continued duking it out with the bad guys, to avoid joining their ranks and worshipping the fallen one.

Ingame sightings
Images of Satan, Beelzebub, or Baphomet can be found throughout the series on stone work, especially after entering Hell.

The name Satan Appears in the ending of Classic DooM's unofficial 5th Episode: Sigil, Where It is explained Satan had bade Baphomet to bring Doomguy back to hell without realising that doomguy was the reason the invasion on Mars failed.

''Baphomet was only doing Satan's bidding by bringing you back to Hell. Somehow they didn't understand that you're the reason they failed in the first place. ''

''After mopping up the place with your arsenal, you're ready to face the more advanced demons that were sent to Earth.  Lock and load.  Rip and tear. "'' Besides this mention, the bosses for sigil are a Spider Mastermind followed by a cyberdemon. Satan,called by this name, never appeared in the game. leading some beliefs Satan and the Icon of Sin to be the same entity in the classic DooM, but that is not confirmed.

In the 2016's reboot of the game It is established that the Icon of Sin is the demonization of the betrayer's resurrected son. Thus hinting that he and Satan are probably different entities. In DooM 2 ingame, DooM 3 and DOOM (2016) "Satan" is not mentioned.