Avalgaith is a Cargûl boss in Carn Dûm. He is in the center of the square directly in front of you after exiting from the top door of the western tower.
Pull each of the Angmarim High Priestess surrounding Avalgaith one at a time. The priests will spawn two Pale-folk. Once the priests have been taken care of, defeating Avalgaith should be pretty simple.
|Bosses of Carn Dûm|
|Urro • Barashal • Helchgam • Sálvakh • Azgoth • Avalgaith • Tárlakh • Târlug • Mormoz • Rodakhan • Múra • Gúrthul • Mordirith|