WARNING: The following article contains spoilers for the series finale of Adventure Time, "Come Along With Me," which premiered Monday, Sept. 3, on Cartoon Network
Adventure Time built up the looming Great Gum War to be the central conflict of its series finale, but the family feud between Princess Bubblegum and her uncle Gumbald turned out to be little more than a the precursor to a larger, existential threat to the Land of Ooo. Its arrival in the four-part "Come Along With Me" confirms plenty of fan theories, while providing few real answers.
War is averted midway through the finale, thanks in large part to the actions of Finn and Jake, only for the sky to open above the battlefield and reveal GOLB, the enormous malevolent entity who's lurked at the edges of Adventure Time, and the consciousness of fandom, since Season 5. So, to all of those fans who made videos and wrote blog posts theorizing that GOLB would be the primary antagonist in the finale: Congratulations, you were right. But who, or what, is GOLB, the foe so massive that his name is in all caps?
The mysterious entity was introduced briefly in 2013 in the episode "Puhoy," in which Finn is transported to Pillow World after retreating into a pillow fort. After living out a long life in that alternate realm, Finn dies and flies through space, only to bounce off the tongue of a red, gargantuan, four-eyed being that tries to eat him on his way back to Ooo. That's, of course, GOLB, who isn't actually named until more than two years later, in the Season 6 episode "You Forgot Your Floaties," in which he's revealed as a malevolent entity (surprise!) who had attacked Mars and abducted Margles, the wife of King Man, aka Magic Man, aka Normal Man (whew!).
It's not until the Season 8 episode "Whispers" that GOLB is mentioned again, when the villainous Lich refers to himself, rather cryptically, as "the ceaseless wheel, the last scholar of GOLB," igniting, well, ceaseless speculation among fans about the nature of the being. The next clue arrives in Season 9's "Temple of Mars," in which Betty Grof announces to King Man that she has a plan to rescue Margles from GOLB and, at long last, save her fiance Simon, better known as the Ice King.