It's really good though, you should try it.
Anyway, at a certain point in the game you encounter a glowing tree lady who gives you half of a white charm
Charms give you various abilities like enhancing your magic or increasing your weapon reach
To get the other half of the charm you need to upgrade the dream nail until it "awakens". Basically all the dream nail does is unlock various bits of the story. "Nail" is also this game's term for sword since all the characters are bugs
After you awaken the dream nail you can use it to unlock the white palace, which is where you eventually find the other half of the white charm
And this place is HARD
Hence the nickname "path of pain"