神秘型博主

Missing, extremely new, or very obvious to obtain.

This achievement has no cultural references in the English and Chinese versions. It is likely specific to the game. The Enigmata is known to spout ridiculousness and write falsehoods, where History Fictionologists mystify history, while Riddlers are obsessed with destroying the certainty of language. It's rather obvious why "Mythopedia" would be linked to such a Path.