First place is to find the lower falls. Run around the left and make a full circle hugging the wall in the center. You should get an update soon. ( 37, 0.5, 0 )
Second Update is in the middle of the caves. You have to venture upward sorta in a spiral climbing up in altitude. About half way up to the top you will get the second update. ( -5, 24, -56 )
Third Update is at the very top and across a little path that will lead down into another cave on the opposite side. The cave has a bunch of coffins in it. This is where you get the third update. I would suggest leaving this one for last. ( 90, 57, -88 )
Fourth Update is near the entrance of the zone. The location is ( 16.15, -1.30, 9.90 ) or ( -11.30, 0, -35.50 ). As you enter the main chaimber head North-West till you see a cave with a bunch of Eventides, turn to the North and walk to the centeral spire untill you begin to sorta swim. You will see the top of the enterance to an underwater cavern. It's not totally underwater either.
This quest can be done in invis all the way through if you have high enough invis and nothing can see through it. You might have trouble with a named fairy seeing through invis. Just hug the right wall from her and you will be fine. Also keep in mind when you get to the top, do not get near "T'rath the Usurper". If you do and he begins talking you need run and get out of there. "T'rath the Usurper" is a very nasty monster. You will need a full group. He's a level 40 double up who Complete Heals himself for full power/health if you can not kill him in a certain allocated amount of time.