Satan

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Satan is God's enemy and is the main antagonist in the Forgotten Series (the Antichrist is the tertiary antagonist). In the series, he is the enemy of God and he is the main orchestrator of Operation Armageddon
==Forgotten: Apocalypse==
Satan is first seen in Forgotten: Apocalypse. He gives a former student named Nadroj dominon over the Underworld while he goes to Earth disguised as a human being in order to deceive the world. However, his plan quickly backfires when Task Force Eagle Claw sabotages a terrorist attack on New York City made by him, in which he attempts to make everyone in Times Square worship him.
Later, Hannah Smith types up a thesis stating that Allah from Islam is really Satan from the Bible, which is later proved to be correct later on; mere days before the assassination of the Antichrist, Satan appears in Mecca, Saudi Arabia, during the Ramadan and calls all Islamic extremists and their supporters to kill the Americans and plunder major American cities in retaliation for "wars waged against the Muslim world". 
==Forgotten: The Mark==
In Forgotten: The Mark, Satan rebels against God again, but is once again thrown down to Earth. Later, he indwelt the Antichrist and then made a pact with him, which stated that even if Satan is outside his body, the Beast would still be able to have satanic powers over the world. Sometime after the Antichrist's resurrection, Satan brainwashes Vladimir Makarov and Solomon Lewis, turning both men into terrorists.
==Forgotten: Armageddon==
Satan reappears in Forgotten: Armageddon. Here, he's seen orchestrating the events of the Israeli Campaign, along with Project Takeover. Later, he forms the United Demonic Army and then personally leads a demonic legion in a full-frontal assault against the Americans during Project Takeover. First, he brainwashes various US military generals to turn them against the US President and then hacks the US military's Drone Army, turning them against the United States. 
Task Force Eagle Claw join forces with Task Force Underdog and fights back in a dramatic battle against the US military's own drones. Despite taking heavy losses on both sides, the Americans manage to win the battle, forcing Satan to go to Plan B; he attacks Israel by opening a portal, allowing thousands of demonic legions to swarm the skies over Jerusalem; God reacts by sending His own legion of angels in order to protect the city while instructing TFEC to assist the angels in destroying the Antichrist's legions.
During the Israeli Campaign, Satan uses the Antichrist to fight against Jesus and His legion of angels at the Glorious Appearing. However, the battle ends in a total defeat for the Global Tyranny, which also leads to the overthrow of the Antichrist; he is cast into the Lake of Fire and Satan is chucked into the bottomless pit for 1,000 years.