The cave is occupied by Falmer and a group of bandits trying to cleanse the cave. A switch just to the left of the stairs on the second level opens the barred gate seen when first entering the main section of this cave where two Falmer are encountered.
Duskglow Crevice is a cave almost due north of the Weynon Stones and about halfway between Fort Dunstad and Silverdrift Lair. Inside are Falmer (×7) and Bandits (×2) (dead ×4) fighting each other, Skeever (×2), Chaurus (×3), a moth in a jar, a copy of Purloined Shadows and a cooking pot.
You are meaningless. Apparently they were meant to be part of a quest. However, instead of being implemented, the quest was canceled, and they either didn’t have time to remove it, or simply decided against it – one way or another, players ended up with the bugs in the jars and a whole bunch of puzzles.
Find the Heirloom
To complete the quest, all you need to do is retrieve the item – although while exploring the dungeon you might end up collecting other loot and killing different ones Enemies.