Warning! Spoilers ahead for Amazing Spider-Man #850
In the landmark 850th issue of Amazing Spider-Man, several big twists occur and major changes happen for the Webslinger, most notably the return of his arch-nemesis, the Green Goblin. It's been a long time since Norman Osborn has donned the classic green and purple duds, flying around on his glider and tossing pumpkin bombs. While the issue reveals that Norman had long been planning a return, the recent attack from the Sin-Eater has forced his hand. Not only that but with so many of Sin-Eaters's followers converging on the two of them, Spider-Man and Green Goblin are forced to team-up and fight side by side.
Spider-Man had already been incredibly conflicted before this issue as to whether or not he should save Norman from the Sin-Eater, and several of his spider allies had warned him against it as there had yet to be any evidence that Sin-Eater's "cleansing" had any negative or lethal side effects. Instead, it merely rendered his victims harmless, causing them to lose their violent and criminal tendencies. However, Spider-Man believes the other shoe is going to drop, and it was therefore his responsibility to save his nemesis, regardless of his personal feelings.
When Spider-Man and Norman get trapped inside Ravencroft in The Amazing Spider-Man #850 from writer Nick Spencer with art by Mark Bagley, Ryan Ottley, and Humberto Ramos, Spider-Man gets caught by a horde of Sin-Eater's followers. Strangely, they all seem to have become something monstrous and beyond human. While Spider-Man is incapacitated, Norman takes the opportunity to take his terrible serum once more, and the Green Goblin is reborn. Not only that but in order to survive, Spider-Man has no choice but to trust his greatest enemy in order to survive.
As they work their way through the mob, Spider-Man has to stop the Goblin from killing the followers, but suddenly they all cease their attacks, kneeling for the arrival of their leader, the Sin-Eater himself. Horribly, Sin-Eater mutated when he took on the powers of the Juggernaut, and it takes the combined forces of Spidey and the Goblin working together to slow him down. Goblin even saves Peter from the wreckage that had temporarily trapped them both, repaying the debt he owed Peter from when Spider-Man saved Norman from his burning lab years ago.
As the battle continues, Spider-Man and Green Goblin remarkably work quite well together (which is pretty concerning for Peter). However, after the duo manages to bury Juggernaut in a large pool of mud that they created from a focused EMP tremor, Spider-Man gets trapped in the mud as well. As he tries to get free, Goblin takes the opportunity to enact his inevitable betrayal, attempting to drown Peter. However, Spider-Man is saved in the knick of time by his fellow spider friends and allies, who were prepared to intervene for this very reason.
Green Goblin's betrayal so soon after his truce with Spider-Man is not surprising in the slightest. Spider-Man should have seen it coming from a mile away. To his credit, Peter most likely never fully trusted Norman, but the circumstances didn't really give him very many options to do otherwise. In the aftermath, Spider-Man now has to deal with the fact that the Green Goblin is reborn, and will no doubt go on to cause more pain, suffering, and torment upon Spider-Man and his loved ones. The cycle continues, no matter how badly Spider-Man wanted to break it with a darker, more permanent solution in the moments of the issue's end.