Agent Coulson is killed by Loki. Barton is released from Loki's mind control and unites with the Avengers. Loki uses the Tesseract to open a portal to space, unleashing the Chitauri army on New York City. The Avengers fight the army, but they're hopelessly outnumbered. The military launches a nuclear missile at the city, which Iron Man throws into the portal, destroying the Chitauri mothership, therefore killing the soldiers. Thor takes the Tesseract and a captive Loki back to Asgard for judgment. The Avengers part ways, but Fury suggests that they will be needed again. During the credits, we discover the real mastermind behind the Chitauri: Thanos.
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Continuity mistake: Throughout the film, Tony Stark's chest ring can be seen glowing through his shirt except for two occasions when it's suddenly off - after Loki escapes from the helicarrier, and when Loki and Tony Stark are talking in Stark tower, even when he's wearing the same shirt. (01:35:30)
Natasha Romanoff: This is the Tesseract, it has the potential energy to wipe out the entire planet.
Bruce Banner: What does Fury want me to do, swallow it?
Trivia: When Loki is grabbed by the Hulk and repeatedly smashed into the floor, Tom Hiddleston had a rope tied around his ankle which was pulled to achieve the effect. Although, Tom was told that the rope would be pulled while speaking to the Hulk, he was never told when the rope would be pulled so his reaction to quickly be pulled down was real.
Answer: While Loki is not immortal, he's just as powerful as Thor, and many mortals would consider him a God as well. Loki is actually a Frost Giant taken in by Odin, but is just as invulnerable to many attacks. There may also be an element of magic involved in his survival as well.
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