"Lost" spoilers from season 6 might seem a bit late at this point, but they might still be necessary for anyone that has ever missed an episode. After all, the final season was so tightly plotted that it became difficult to miss even a single scene. Thankfully, the spoilers below can help any viewers catch up quickly.
Brotherhood. Jacob and the Man in Black made their first human appearances late in Season 5. Their relationship was more or les unknown, though many ventured a number of different theories. The spoiler, of course, is that they were simpl brothers.
The Island's Master. Jacob is much, much more than just a mysterious figure. He was, in fact the master of the island itself. Much of the drama of Season 6 revolved around finding his replacement.
Adam and Eve. When the "Lost" crew first discovered the cave, there were two skeletons. Nicknamed Adam and Eve, they were seemingly forgotten. The final episodes revealed the bodies to be those of the Man in Black and his adopted mother.
The Island's Purpose. The mystery of the island has always been the central mystery of "Lost". This spoiler should, be all rights, be fairly game changing. Unfortunately, it turns out that the island was merely meant to stop a mysterious "evil" from escaping.
Going Home. The bomb that went off at the end of Season 5 seemed to have made major changes on the island, but nothing that viewers could see. Instead, "Lost" viewers were then treated to "flash sideways" of a universe wherein the "Lost" cast made it home. Even this, though, seemed to be a bit more than meets the eye…
John Locke. Viewers knew that John Locke had been killed. It was even known that he had bee taken over by the Smoke Monster/Man in Black. His form seemed to have a great deal of effect on the final enemy of the show, though, as a few moments hesitation allowed him to finally be felled by Jack.
Betrayal. Betrayal has always been a major theme of "Lost". The Man in Black seems to be king of the trope, though. Sadly, his destruction of the submarine left "Lost" favorites Sun, Jin, and Sayid dead in the water.
Desmond. Desmond has been an odd character on "Lost", ever since his first introduction. Season 6 finally let viewers know why he was special. It is not his time jumping ability, but rather his resistance to electromagnetism.
New Man in Charge. Who replaces Jacob? We are led to believe it is going to be Jack, the closest thing to a main character that "Lost" has. Instead, it ended up being Hurley.
Purgatory. A popular theory about "Lost" has always been that the island was Purgatory. The theory was, of course, flatly denied up to and through Season 6. The spoiler? The flash-sideways universe was, in fact, Purgatory all along.