Seek Quetz'lun's Spirit at the Altar of Quetz'lun.
You are prepared, but I'm not certain that you're ready for what is to come.
When you cross back over into Quetz'lun's altar area, you will enter the realm of the dead. From what I can feel of it, it's not going to be pleasant.
Try not to be distracted by what you see in there. Simply head for the altar building and seek out Quetz'lun's Spirit.
You will also receive:
- 10,700 experience
- 63 (if completed at level 90)