|The following information is from the Adventure Time comic book series. It may not be part of the same canon or continuity as the animated series.|
Adventure Time #60 is the sixtieth issue of the Adventure Time comic book.
Finn gets into the dungeon-making scene and meets fellow dungeon masters, some of whom are villains from Finn's past!
Sometime in the past, a father and daughter are outside at night. The father tells his daughter that she should look at the moon through their telescope. The daughter asks about aliens, and her father tells her that there is nothing scary on the moon. When she looks, however, she sees a dungeon statue which freaks her out. She pushes the telescope into the water below and says they shouldn't go outside at night again. On the moon, Finn is crafting the dungeon for the Blade of the Defender, singing as he does. He seems unnerved at having to be alone for hundreds of years. Suddenly, he hears voices on the station's radio. They ask if anyone is there because of Finn's weird structures. (They also think they may have made first contact with an alien and get upset that their odd conversation might be immortalized.) They plan on sending a crew to investigate. Finn is worried about people coming to the moon, so he answers by pretending to be a computer that was left on. The people seem to believe it and tell him to go into sleep mode. First, Finn asks if anyone is coming to the moon. They say yes, but not for years. Finn thanks them for telling and pretends to go into sleep mode, running out the station. However, the people know he was a person and not a computer.
Years later, three astronauts are dispatched to the moon. After landing, ground control tells them they can relax after docking with the base. The astronauts instead decide to see the weird structures, to which ground says they have protocols. They enter the dungeon excited, but one of them accidently triggers a trap. A statue fires a laser that just misses him. They decide to either study that or keep exploring, and go with the latter. They find the Blade of the Defender and the same astronaut who set off the trap tries to touch it. The sword turns out to be an illusion and he falls down onto a catapult, which flings him off the moon. The other two hurry to the rocket to save him, informing ground as they go. Ground tells them that they only have enough fuel for one launch, so they must return to Earth after the rescue. Finn, now old, saw everything happen and is pleased his dungeon did well. As he enters the station, ground sees him on the monitor and says to him that he must be the alien. Ground is actually Davey, who comments that Finn looks like a human. Finn clarifies that he is human and says Davey looks familiar. Davey thinks the same about Finn.
After introductions are made, Davey asks about the astronaut being shot into space. Finn says his dungeon did it, prompting Davey to ask about that. Finn tries to explain that the moon is part of an ancient being who sacrificed itself to be used as a weapon against other bad ancient beings. He is protecting a sword that is important to it all and requires the right person to come, so he made a dungeon to keep it safe. He also says that he's from the future and that Davey is the first person he's talked to in years. Davey thinks Finn is reasonable and agrees to cooperate with him. Finn tells him the prophecy of the sword, which is that the wielder can be harmed but not hurt (he doesn't remember well since he read it a long time ago). The sword won't work if the user is hurt. Davey says he can code some security in the base to prevent those who are hurt from going out, which Finn thanks him for. Davey says they won't send anyone else to the moon and signs off. Finn realizes that this is why the base wouldn't let him out as a kid, calling it a paradox.
He thinks the day went well, but knows that a portal connecting the base and Ooo will appear one day, and his younger self will take the sword and throw it into the ocean. Then he would have to retrieve it and make young Finn go through another portal to build the dungeon. But he is old and the oldest people he ever knew may not have been born yet. He doesn't know how he'll live that long, but the pot full of youth elixir suddenly appears above him (and falls on him). Finn eats some of it and becomes a teenager again. He sees it as enough juice to keep him young for a really long time, then questions where it came from.
Back in present-day Ooo, the three ancient beings continue destroying the land. Jake has put his youth into the pot, which was sent through the same time portal. Princess Bubblegum thanks him for his sacrifice. Jake hopes it gets to Finn, and Peppermint Butler says it will, as foretold by crazy magic. Jake wishes he could be with Finn, and Bubblegum and Peps both think it would be okay for him to go since he helped them find the portal. However, the ancient beings enter the temple, thinking it and everyone inside wold taste good. Jake tells Bubblegum to run to the sanctuary as he holds them off, and Arklothac tugs on him. Bubblegum asks if Jake will be at the sanctuary later, but Jake says it's unlikely, as his old age makes him less stretchy. She tells him to come with them, but he tells her that all the candy people need her help. Bubblegum thanks Jake for his help and bids him goodbye, leaving him to his fate.
Farther into the future, Penelope's companion Betty wakes up from a bad dream. Penelope tells her that they are around the edges of old Ooo. They are hiding from someone who won't be there and should move on. Betty gets restless and runs back to the Candy Kingdom. Penelope pursues, saying they checked there already. The ancient beings notice something running through the woods and feel like eating it. Penelope is worrried about being spotted, but follows Betty into a cave. Betty finds a portal and goes through it, so Penelope goes after her. On the other side, Penelope realizes that they are now on the moon. After ptting on a spacesuit, she goes to the duungeon and gets the Blade of the Defender.