Nasty Dungeon is a location and a optional dungeon in Final Fantasy Legend II. The dungeon lives up to its name. The monsters come in a large variety of groups, and the dungeon's branching pathways offer no real indication as to which path is the correct one. Enemy groups can easily reach up to fifteen monsters per battle, and surprise attacks can become quite a constant threat inside this dungeon. But the treasure found inside is well worth the effort.
Immediately upon entering, there's a fairy present standing right next to a treasure chest containing the only MAGI in this world and when the player collects it, they are perfectly free to just go to the next world. The fairy inside advises the party not to proceed into the dungeon.
When the party arrives at the end of the dungeon, the same fairy they have seen at the beginning stands between them and the exit. She says the dungeon was nasty, and asks if they agree. Answering yes will make her leave, while answering no will cause her to send the party to the middle of the dungeon.