The runix cube is put together by different pieces. Go to Mobius and finish The quests at the gate to be given approval of getting into the inverted building at the entrance. Enter the building and talk to Anna and Otto to recieve the first piece and info on the next pieces. Complete the Fairy's quest to recieve the next piece. Recieve the last piece after completing the quests given at the gate. Put together all the pieces in the puzzle to finish the runix cube.