A Blank teleport crystal is given to the player by Arianwyn, leader of the rebel elves, at the beginning of the quest Within the Light. The default left click option is to "Chant-to" the crystal, which can only happen when standing at a certain point outside of the Temple of Light. If the crystal is clicked on when not standing in that location a message appears in the chatbox that says "The crystal doesn't seem to respond at all here."
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