Invasion took place in the kingdom of monsters Ooh. The game "Adventure Time: Music Castle 2" will tell you the story of this event. You will be directly involved in the battle, which will save the kingdom from invasion if you can cope with the monsters invading your land. You can fight them through sound that will impress any monster, but keep in mind that each of the sounds is against a certain monster. Go through training and be able to quickly figure out how to destroy them.
