Upon completing Riddle of the Vault, you received a note and a crystal. The note is from High Priestess Harla Dar to Cyenadros which states:
"Cyenadros, see to it that this crystal is destroyed after viewing its directive. We cannot have just any earth walker prancing in here and dunking this gem into the spirit pool. - High Priestess Harla Dar of the Awakened"
Inspect the crystal of command. You are told to find a place where the crystal will do something.
Go to the Pool of Spirits( 152, 41, 146 ) /waypoint 152.4, 41.1, 145.5, and jump into the pool. Examine the Crystal again to get the first update.
The crystal definitely has magical properties, if not some form of creature inside of it. You are told to toss the crystal into some sort of pool of apparitions, ghosts, ancestors, spirits or something!
A certain spot on the Pool of Spirits can be interacted with, using your mouse pointer. Right-click and throw the crystal into the pool.
The quest will tell you to speak to the spirit. You will be on a timer. The Voice of the Palace has spawned at the bottom of the pool. Just hail him to get the next update. You have 90 seconds to hail him after throwing the crystal into the pool.
Return to Murrar (good-aligned) or Tayil (evil-algined) in Tenebrous Tangle in the Hidden Refuge.
Note: if you betray your toon anytime before starting this quest you will be unable to complete it as it will send you to the wrong NPC, who will not talk to you.