If you check the quest this mob is tied to, you can see the following comment:
Quote:
Then head to Akheva Ruins and kill the Sacrificed Remains inside the Sacrificial Pit. They are PHs for "A Shimmering Presence" and have a respawn time of about five minutes.
Now, look at the picture here. In the upper right corner there is what appears to be a dead mob on the floor, and you can read enough to know that is a "Sacrificed Remains".
I hope this helps people figure out how this mob appears. Unless thye have changed the process of getting this NPC to spawn.
If someone accidently kills shimmering presence he won't spawn anymore. Don't know how long till he will start spawning again. Trying to find out. Some say 3 days some say a week.