こんなものが試練なのか

Unlocked after completing the previous 15. As of the latest update, there is still a bug that makes you unable to obtain this achievement if you solve any new puzzle before talking to the NPC.

A reference to the Rubik's cube and how difficult it is to solve for some people; you get this achievement after solving 15 new Hexanexus puzzles (Hexanexus bear a resemblance to the Rubik's cube, but are much simpler). - Credit: Raiden