The Defenders battle Satan and his fellow Hell-Lords, but even that showdown pales before the ultimate hellish duel: Daimon vs. Satan, son vs. father!
Satan explains that all the problems the Defenders have been having recently have been part of his plot to take over the world, from Eternity's problems to the Six-fingered Hand and Hellcat's possession.
Some of the Defenders try to attack, but are repulsed by the newly-demonized Hellcat. Satan reveals that Hellcat is his daughter, to the shock of the others.
Satan explains that while his son Daimon has been a disappointment, Patsy will be a true daughter of his evil. He says that he amazing agility, which she realized in issue 83 was not due to her costume, was actually due to her demonic heritage. Her best friend, Valkyrie, tries to persuade her to reject this, but she says she was never her friend.
The other major demons in attendance--Mephisto, Thog, and Satannish--variously called Satan's brothers and his other manifestations--hope he gets on with his endgame: once in a while, the universe allows the forces of evil a chance to take over the Earth. It takes 6 days, 6 hours, and 6 minutes to achieve, but if successful, they will be in control for a dozen ages.
He gives the Defenders a deal where if they can defeat the other demons in certain trials, they can save Earth. The Defenders agree.
Hulk, Namor, and Dr. Strange end up reliving a scene where they fought the disciples of Dormammu early in the Defenders' career. Namor and Hulk get separated from Strange, and are attacked by recreations of Xemnu and Yandroth, who defeat them. Strange finds them and Satannish, and almost saves them when they are all killed in a volcanic blast.
Satan tries to seduce Daimon Hellstrom over to evil, while making him recoil at the concept that he is in love with someone he know believes to be his sister.
Nighthawk, Gargoyle, and Devil-slayer are in the middle of a giant battle, where the soldiers are warriors killed in wars throughout time. They taunt Nighthawk, who didn't get drafted due to his bad heart, Devil-slayer for the war crimes he engaged in in Viet-nam, and Gargoyle for the fact that his friend died in World War I, but he survived. Nigthawk manages to persuade the dead soldiers to join them, but then Thog kills them all with four nuclear bombs.
Satan tells Daimon he must choose to join him, or suffer in hell.
Clea, Valkyrie, and Silver Surfer appear in a blank space. Mephisto tempts them all with their desires, but they reject his overtures. They seem to defeat him, but then they are dissolved into the space.
All the Defenders, having lost, appear back on Earth, where time has passed, and Hell has almost taken over. Satan orders Patsy to kill Daimon. They battle, and Daimon almost kills her, but his love for her keeps him from doing it. He now challenges Satan; Satan accepts if the Defenders agree to keep out of it. They agree. However, Daimon is no match for him, and Strange and the Defenders send him their energy to enhance Daimon's darksoul, breaking their oath and making Daimon more evil--the only way he can win. Still Satan defeats him again, and almost kills him.
However, just as Daimon could not kill Patsy due to his love, Satan cannot kill Daimon due to his love for him. In finding the light in his darkness, Satan agrees to leave. Daimon, now evil due to the Defenders' intervention, agrees to join him after all. Satan releases Patsy from her demonic form. As he leaves, Satan taunts them, saying that perhaps Patsy is not his daughter after all; maybe all of this was a plan to get his son back, or a plan to make the Defenders lose their purity by going back on their oath; or maybe he really was defeated by them after all--there's no way to know.
The Defenders, however, feel at least some comfort in knowing that they saved the world from hell.