From Aura Kingdom Wiki
[insert game's description here] The Dimensional Hall is available once per day and gives a generous amount of experience.
1. Accept the quest from the Dimensional Mage outside the Dimensional Hall entrance. You will be given a stone which will unlock one of the crystals within the Dimensional Hall. Your friends should accept the quest as well, and then they will also unlock the remaining crystals inside the Dimensional Hall.
2. After all 3 crystals have been activated, monsters will spawn; kill these monsters. After the final monster is defeated, you can return to the Dimensional Mage outside of the Dimensional Hall.