I would just like to add to this, as I was really wracking my brain trying to do this on my durge playthrough. It is *technically* possible to have the Emperor kill Orpheus, and then betray him in the end (an opportunity, perhaps?). However, Lae'zel will not be able to ascend in this scenario as she becomes enthralled by the Absolute. The only companions who will not become enthralled are Ascendant Astarion and Minthara.