Sep. This could be a nice opportunity to make the relics of Thora and Kheris similar in function (but not identical). Sort of like how two inventors independently make a thingamajig to do the same thing, but have opposite approaches to the task.

We're thinking that our darkness-weaving NPC will still exist, but not necessarily survive the taking of Amaryth. His power, while intangible, is still very useful. That in itself is a reason it shouldn't be too readily available.