I currently have an issue with this mission in which I have gone into the worm's retreat killed the skeletons down to the bottom but in the last bit Aldimion, the enemy at the end, has been invisible and invincible, killing me should I get in the area. As I was typing this I fixed it by logging out then shutting the game down to restart, but figured this post would be useful if anyone encounters it or if the game developers think this can be fixed easily.