Kill Druzan - he's an lvl 28 Epic x2 Drakota. Slightly underconned but still an epic - a group of 3 players with mercs should probably have enough dps to burn him down, but good luck finding a group at that level for this zone.
WARNING: The journal difficulty for this quest appears to be normal(!) (as do all the parts of this quest sequence). However, it involves multiple fights vs mobs rated Epic (x2), so beware!
Players above 60 can 1-group this. Some players can solo it at 70, depending on class and gear.
Ghagan may aggro you even if he is greyed out. See The Discussion. Running to the base of the stairs is the trigger for him to attack. If you do not want to kill him follow the steps listed in the quest Revelation.
Go through the doors (your quest will update here) and across the rampart to ( -112, 24, -93 ) /waypoint -112, 24, -93. Kill Rygia (54^^^ Epic x2 Necromancer) assisted by Advisor Kal (54^^^ Epic x2 Warlock). The quest will update and you will receive Rygias Amulet of Dousing with 12 charges.
Go back through the doors and turn left. Go up the ramp until it reaches a circular hallway. Turn right and go around to a set of doors on the north wall ( 0, 41, -384 ) /waypoint 0, 41, -384. Go through them and follow the cavern to its end.
Inside Kodan's cave are two idols. Approaching one will give you the chat box message, "You see what appears to be the word Rygia inscribed on a strange idol." These idols cause "beams of soul-sucking energy" to strike the party and will continue to do so as long as Kodan is alive. Use Rygias Amulet of Dousing to turn off the idols briefly. When they reactivate, you will receive the chat box message "The strange idol has been reactivated" if you are still standing near one. Continue using the amulets to turn off the idols while fighting Kodan.
The idols have unlimited range through the entire instance, and do not require line-of-sight. This means that if are solo & you die and choose to respawn at the front door, they will immediately start hitting you for massive damage every few seconds and stunning out all your abilities to boot as well as rooting you. You get only brief intervals to heal up & move between attacks! You can't disable them until you're near them again. It is quite a trek back to Kodan's cavern, although it is possible to get there & resume the fight. However, it would likely be easier to exit the instance and wait out the lockout to try again. You won't need to kill Rygia again, at least.
If you linger in the zone after killing Kodan, you will eventually be attacked by Diamondon 55^^^ Epic x2 grouped with 2 golem guardians 55^^ Epic x2 (KB, stun, cold, crushing). They will eventually be joined by The Dark Planner, 55^^^ Epic x2 drakota (poison, divine, slashing).
Return to the NPC you received the quest from for your final reward.