What is the Mystery Key for in Undertale?

Best Answer

The Mystery Key unlocks the door to Mettaton's house in Napstablook's neighborhood. You'll find some interesting lore there!

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DepetallingMummy·3 months ago

Mystery Key? Just get it and find out yourself! Adventure is the best teacher!

CorrectingGait·3 months ago

It opens up the locked house next to Napstablook's in the Waterfall area, revealing a bit more about Mettaton's backstory. Totally worth checking out!

ColoringNoon·3 months ago

I've used the Mystery Key myself. It opens Mettaton's house, which is right next to Napstablook's house in Waterfall. Trust me, it's a must-see!

👀 If you like Undertale...

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