There’s a secret Paper Mario: The Thousand-Year Door party member you can unlock if you put in a bit of effort, but the classic RPG does a pretty good job hiding what you need to do. She might not be much help in combat, but her field skill is one of the most useful in the game--especially if you’re keen on tracking down every secret.

We explain how to unlock the secret character in Paper Mario: The Thousand-Year Door below and whether she’s worth the effort. Of course, be mindful that this guide is one big spoiler.