Critadel help?

Been playing Critadel on Switch recently, since I want to unlock the Curly Brace alt costume for Nox. But the game is too obscure, there's virtually no info online of it, much less what I'm looking for. In-game, the alt used to say what you needed, but that changed to "???" at some point. I figured this might be the best place to ask, since the "Cameos & References" lists it.

Please, somebody help me.