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.
A new Drakota named Kodan spawns and tells You shall never succeed. We will defend the artifact at all costs! Kodan voice resonates across the land: Idiot rats! I have lost all patience with you, I shall brook no more failures! Kodan continues: Dispose of these vermin once and for all, or answer to me!
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 at ( 0, 41, -384 ) /waypoint 0, 41, -384. Go through them and follow the cavern to its end.
At approximately ( -43, 19, -726 ) /waypoint -43, 19, -726 an ice collossus will attack you, even if it is gray.
When you reach the end of the cavern at ( -124, 14, -633 ) /waypoint -124, 14, -633 you'll come upon Huyzak the Cunning and Bresellis the Dark, with three roekillik guards. This is the start of a very difficult fight. Huyzak the Cunning must be killed last, because his death triggers an event. The wall behind him will explode and a large drakota will come bursting through.
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 as well stunning/rooting you. You get only brief intervals to heal up and move between attacks! You can't disable them until you're near them again. It is quite a trek back to Kodan's cave, although it is possible to get there and 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 and then the Dark Planner.