|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 #61 is the sixty-first issue of the Adventure Time comic book.
Finn becomes a bit obsessed with building his perfect dungeon, losing the plot a bit, and toys with terrible and great evil forces to build his ideal dungeon understand Joshua better through dungeoncraft.
Far into the future on the moon, Penelope has claimed the Blade of the Defender and is amazed that it can shoot lasers. Then she sees Earth still being devoured the ancient beings. She isn't sure a cool sword will be enough to stop them, and Finn pops up asking if the coolest sword would, surprising her. He tells her that he used that sword to defeat Arklothac once. Penelope asks why the ancient beings are still around if Finn was successful, and Finn says it wasn't a total success since Arklothac came back. He then introduces himself, and Penelope introduces herself and her tigercorn Betty, who states that she is her own tigercorn. Finn explains that the sword wasn't meant for him, as it stopped shooting lasers if he was hurt. Lun, the benevolent ancient being (whose name he can now pronounce), told him that the sword is for a warrior who can take great bodily harm without injury, probably because stopping all the others at once is important and getting hurt in the middle of a battle is problematic. Finn believes Penelope to be the one, as she made it through his dungeon. He asks if she's ready to save the world, but she tells him that she has been injured before a lot. Finn declares that they'll try anyway because he is really tired of waiting on the moon.
Penelope wants to help, but is worried the sword is too small for the fight. Finn reveals that after building the dungeon, he built amplification devices using the additional knowledge Lun gave him. They get on the device and Finn tells Penelope to fire the lasers with it to stop the ancient beings. She decides to try, although she thinks they'll be very mad. A mighty blast is sent through Zon, destroying it off the sun. Arklothac and Ng'zot Aa see that Lun's weapon has a wielder and go after them to avoid being killed. Finn tells Penelope to keep firing, but Arklothac quickly arrives and destroys the amplifier, questioning who is confronting them. Penelope says she is and that it won't matter to them soon. She admits that she's terrified, but Finn says that her trash talk helps. Arklothac says it doesn't and chops off her arm. Finn is worried, but Penelope says that it's bionic and that she's fine. Seeing her as injured, Finn thinks it's all over and apologizes for putting her through it. He suggests they negotiate as Arklothac picks him up. Arklothac recognizes him as the one who banished him before and wants to cook him. However, Penelope denies him this by destroying him with the sword's lasers. Finn thought she was hurt, but Penelope tells him that she didn't feel anything from her bionic arm. She then destroys Ng'zot Aa. With the ancient beings gone, they break for a lunch.
They all return to Ooo afterwards, Penelope's arm repaired, and Finn notes that it's different from what he remembers. He thinks the ancient beings might return again as long as the sword, a part of one of them, remains. For a solution, Penelope pulls out the jar of goo she carried with her, which Finn says looks familiar. Penelope says she got it from under his old house, making him ask how she could know him. She says that she is a later incarnation of him, and looked in the book of their past incarnations for clues on stopping the ancient beings (whose name she can't pronounce). She also tells him that the "weird crystal goo thing in another dimension" is what made the portal to the moon. Finn gets a feeling that the paradox they're talking about will pull him back in time. Penelope then tells him that the goo is really primordial ooze, pure spacetime, and that whatever touches it is wiped from all existence. Finn can't remember why it sounds so familiar, but they realize that throwing the last remnant of Lun in it will make it as if the ancient beings (whose name Penelope manages to pronounce) never existed. They say their goodbyes and Penelope drops the Blade of the Defender into the primordial ooze portal.
Penelope and Betty find themselves in a forest. Penelope asks what she was doing, and Betty tells her she was looking for the ones in hiding. Looking at her amulets, Penelope remembers she is looking for Bubblegum. In the present, Finn asks what he was doing while wielding the grass sword. Jake tells him that he was performing a ceremonial sandwich cutting on a very long sandwich Jake made for all of Ooo. Finn finishes the ceremonial cutting and everyone starts eating. Gata appears asking to join in, and Jake lets her. She and Finn introduce themselves to each other, and she asks if they eat giant sandwiches everyday. Finn says they don't, but Gata still likes a culture that might do it occasionally. She says she escaped from a bad dimension because her evil mother forgot how to use magic. Finn and Jake agree that bad dimensions are bad. Finn says that Ooo sometimes has a hiccup, but the fun never ends.
- This is the last issue written by Christopher Hastings, as well as the end of the story arc started in issue 36.