"High Harper and Mummy Lord"
Durst was first encountered deep within the The Court of Bones, in where he served as the final guardian of the dungeon, guarding a pillar of shadow covered bone, with a beating oversized heart serving as the pillar’s center.
It was revealed over time that this Heart was the Mummy Lord’s heart.
Now, Durst seems to be serving as the headmaster for the newly reformed Harper’s Guild, and seems to have a working relationship with Alister, who may or may not have known of Durst’s importance when the party first encountered him.
He spoke of being enemies with the Mages of Saruun.