Earthtear Caverns are a large underground network of chasms and tunnels inhabited by spiders, rats and common wormmouths. It plays a brief role in the main quest, as Skelos Undriel insists you cleanse the caverns of vermin to create a secure place for him to stay before he will give you more information about the Shadow of Conflict. This quest can however be bypassed entirely by clearing the dungeon out beforehand.
Additionally, Earthtear Caverns also plays a role in several sidequests, linked below. It can only be accessed from Azra's Crossing.
The caverns get their name from the huge rents in the earth that dominate the area. There are two chasms, each of which is crossed by one rocky bridge. The main enemy in the caves is spiders, so it's lucky that the Spider Impaler can be found in a chest in the northwest.
The level's Shadow Gate is somewhat unusual in that it is invisible. Approach it without the Spider's Shadowkey and you will receive the message:
"Your shadow distorts and twists on the floor. You feel as if someone stabs your neck with an icicle. 'You have neither my permission, nor the key,' rasps a voice. 'You may not enter.' An unseen force blocks your way".
If you approach with the key, you are told:
"Your way is blocked by an unseen force. A whispery voice says, 'You...,' then disappears in a shrill shriek. You may now enter the room".
† Only appears here after a related quest is completed