|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.
The Ancient Enchanted Oven is a sacred artifact that can create beautiful, magical and powerful items. However, only a very skilled individual can use the oven. After generations of neglect, the oven was lost to the Candy Kingdom. Prince Gumball spent his entire life looking for it and found it in a dungeon under his castle. Once he had found it, Gumball used the oven to create Fionna a new, magic sword.