Papulatus' key is not usable here right now. If you head over to the Origin of the Clocktower, then you may be able to find the machine that uses this key. Can you please head back there?

Please find the clues behind the key at the Origin of Clocktower.

Are you deathly afraid of Papulatus?

Hey, how did you get in here?? And who are you? Wait, that key you have in your hand... I have that too... how do you have that? There should only be one key of this kind in this world...

Please show me the key that you have in your hand.

It is the key I have with me. How is it that there's two of its kind?? This is strange.