From the entrance go straight through the first room, cross the bridge and take a left, climb up the first stairs and take a left into the courtyard. From the courtyard, go to the door straight across (named to your left; be careful). You can cast invisibility to get past the skeletons.
You will need to kill the skeletons in the scrying pool room. You will even need to kill them if they are grey - as soon as the water construct spawns, the skeletons will attack and one-shot it.
Click on the pool. (Doing so will break invis) and a water construct will appear.
Continue trying to Dominate the elemental and eventually Kel'dur (level 80 ^^^) will pop.
You may fail to spawn Kel'dur before the elemental despawns. When this happens, clicking on the pool will result in the message "The power in this well has been momentarily depleted.". The respawn time on the pool appears to be the same as or close to the room respawn time, so wait for the room to spawn, clear the skeletons and try again. (I've done this twice now. The first time took at least five respawns. The second time, for my own conjuror, took two, with Kel'dur appearing almost immediately on the second respawn.)