Zarathos is a demon first brought into the mortal world by a Native American priest named K'Nutu to help his tribe in exchange for souls.
Zarathos is a Marvel character created by Gary Friedrich and Mike Ploog, first appearing in Marvel Spotlight Issue #5.
First brought forth from Hell by a tribal sorcerer, Zarathos was deemed too dangerous a rival by Mephisto and was contained in the Soul Chamber before being bonded with mortals, most notably of which would be Johnny Blaze. Wanting to be free, Zarathos sought to obtain the powerful Medallion of Power to rule Hell (and Earth) and whilst continuing to feed on the negativity of souls required for his strength and power levels, would align himself with various demons in attempts to reach this goal.
Major Story Arcs
Zarathos fought the ancient Spirits of Vengeance and corrupted some of their overseers, The Blood. The Blood siding with Zarathos were promised greater power and were referred to as The Fallen. They were betrayed by Zarathos who instead used them to increase his own power in order to challenge Mephisto for ownership of his realm. Mephisto tricked Zarathos using Centurious whose lack of a soul made him immune to many of Zarathos's attacks and with his followers abandoning him, Zarathos was easily defeated through the use of magic and turned into a statue .
Mephisto would also force Zarathos to bond with mortals as a means of containing him, somewhat like the Spirits of Vengeance and for a time bonded Zarathos to Johnny Blaze. Zarathos was released for a short while by the Beyonder but during a final battle with Johnny Blaze, Zarathos was defeated and became trapped in the Crystal of Souls with his old enemy Centurious for all time.
Zarathos later appeared having hidden inside Centurious before being freed by Lilith. After defeating Centurious, the two pursued the Ghost Rider Johnny Blaze and Vengeance but were easily defeated and thrown into the Darkside dimension. Later Zarathos and Lilith escaped the dimension and planned to take over Earth by stealing the Medallion of Power with the aid of the Lilin army and creating the Siege of Darkness. During the siege, Zarathos and Lilith had a romantic relationship although he would have little memory of this before once again being defeated, this time by the Midnight Sons.
The Fallen returned to assist Zarathos and with their help, Zarathos became stronger and embarked on a quest to rule the world. During this time he managed to kill the Ghost Rider Danny Ketch, however the destruction of The Fallen during this battle weakened Zarathos which allowed Blade to use the Justiciar to stab Zarathos, thus transforming him back into a statue. It's been revealed Lilith is pregnant with Zarathos' child who she swears will avenge its father in the future. Presently Zatharos has been bonded to a female mortal who continues to search the mortal world for souls to send to Hell.
Powers and Abilities
Zarathos has Elemental control, is immortal, and has vast superior physical attributes when compared to humans. He feeds on the negative energy of peoples souls to grow stronger and can only be harmed by magical weapons. Due his bonding with Johnny Blaze, he is also an accomplished biker. But the true extent of his powers hasn't been explored and as Dr. Strange said his powers are boundless and God-Like.
When Reilly Tyne, the son of Ben Reilly (Spider-man's clone) and Elizabeth Tyne, was a child, his inherited powers began to kick in, but brought with them clonal degeneration. Kaine, the degenerated first clone of Peter Parker, found him, and placed him within a regeneration tank to slow the process. Trying to kill two birds with one stone, and resurrect Daredevil - who had previously died saving Kaine - while healing Tyne, he summoned the demon Zarathos. Zarathos attempted to possess Tyne, but he was saved by the soul of Daredevil, who drove out Zarathos, although both Daredevil's soul and a piece of the demon remained within Tyne, and he was left with a demonic appearance and certain demonic abilities.
Zarathos later took possession of several members of the Order of the Scrier in an effort to eventually reclaim Reilly's body. However, his main host was destroyed after an explosion during a final battle between him and Darkdevil. Following Reilly's near fatal injuries at the hands of the "new" Venom, Zarathos tried to regain control of Tyne's body but was repelled with the help of Dr. Strange and Doc Magus. In doing so, Zarathos almost lost all his connection to Darkdevil. As a result, only Zarathos' powers were left behind for Tyne.
In Ghost Rider: Spirit of Vengeance Moreau explains Johnny Blaze that the demon in him was once the Angel of Justice. He protected humans but was captured by demons and taken to Hell were he was driven crazy and corrupted to turn into the Spirit of Vengeance. This entity then exacted disproportional punishments on Human Beings for even the least sins.