Talk to Thenon the Wise in the Cultists cave. The same cave for the level 43 Royce Sandstalker (Tomb Keeper) and the Lvl 45 Side Quest - Guard Parilin ( Akuion )

The cave is located on the river bank going North from Forkwatch.

Thenon the Wise is located deep inside the cave. To get to him take a right in the 1st room. The Burrow Cultist can see thru invisiblity as does the Eldrich Ghoul.

Thenon tells you his story of being a king from ages past and that his soul has been trapped in a gem by Lothaxe the necromancer. Thenon asks you to rid the world of Lothaxae and free his soul from the gem.

To do this you must use the staff that Thenon gives you and find the 2 missing essence gems. The essence gems drop from a Ghoul Reaver and Amandon. Both of these mobs are somewhat rare spawns and you may have to clear the room a few times before you ever see one.

To get to the Amandon... from the 1st room take a left, then where the hallway splits, go left.
This is the same room Akuion (lvl 45 Side Quest - Guard Parilin quest) spawns. Akuion is a triggered spawn, so unless you are up to that point in the quest, don't wait around for him.

To get to the Ghoul Reaver... from the 1st room take a left, then where the hallway splits, go right.
This is the same room where the Tomb Keeper (lvl 43 Quest - Royce Sandstalker quest) spawns. The Ghoul Reaver usually spawn directly on the other side of the room from where you would enter it from the hallway. Can be easily seen and pulled from the hallway without entering the room. This room holds the Tomb Keeper and 3 Burrow Ghouls (2 Burrow Ghouls and the Ghoul Reaver is it's up). As far as I know, these don't see thru invis, but don't quote me on that.

Once you've collected both essence gems you'll need to proceed past the Tomb Keeper room, down the ramp where there is Bile(sp?) Rat or two. They don't see thru invis. Past the room with the rats there is a Golem Statue.
Interact with the statue and place the staff in it's had. Kicking the statue will teleport you to the cave entrance. After you pass the statue, keep going to the last room where Lothaxe is. Lorthaxe is a triggered spawn. Spawns after the statue has crumbled to the ground, so you can't do the log out - log in trick to pass the statue.

This room is also occupied by several Burrow Ghasts, but Lothaxe can be pulled from the hallway if you're careful. There is alo another Golem statue in this room. If you interact with it and twist its arm, it will teleport you back to the entrance of the cave. Lorthaxe (level 45), like any good necromacer has a spetre pet to aid in your defeat.

After you've killed Lothaxe and his pet and loot the gem, you'll need to take the gem back to Thenon. Use the statue and start back at the entrance or backtrack the way you came, either way it's a more battling to get back to Thenon.

For all your hard work your reward is a crown and 2.5M exp. Crown of Wisdom: AC 78, Wis 35, level 40, Lore. Usable by Tank, Melee and Healers.