Chapter 5: Mordirith's Fall  

At the start of the instance, all you have to do is kill some fairly easy mobs. Once you enter the throneroom, after some dialog, you have to kill the ghost of Golodir's daughter. Golidir and Mordorith will then have a battle.
Periodically during this battle, the girl ghost will reappear.
The general strategy seems to be:
1) Only attack Mordorith when he's down on one knee (vulnerable). If you attack when he's "active", you won't be able to hurt him much, he'll stop fighting Golodir, and come after the party.
2) When the ghost reappears, all switch to her and kill her. Alternate between
Morodith and the ghost
3) Mins and LM's make sure Golodir stays alive.
4) Since Morodith won't attack the party (unless attacked first), DPS is important
5) Two or more of your party need to have tokens or you'll spend half your time cowering and won't kill Morodith or the ghost fast enough