I've encountered a pretty severe bug completely limiting my progression. I reached the quest where you have to kill the bandit lords, but for the first bandit lord Oak, I chose to help him. A little while later, my friend and I were exping and we ended up killing Oak anyway, but I died during the fight and was outside of the gate. It did not drop Oak's Amulet. I proceeded to go all the way to the end of act 2 at the Dark Altar and we found out we had to go back to kill all of the Bandit Lords. We killed Oak first, again, but it bugged severely and even though we both chose kill I was unable to target or hurt Oak, but I was able to kill my friend. After the fight was over Oak once again DID NOT drop his amulet for me, but did for my friend. We were then unable to leave the arena until one of us died, so I killed him. I proceeded to go through to the other 2 lords and collected their amulets, then we went to the Dark Altar even though I only had 2. My friend had the Apex so we went to see if it would simply advance us both (it did not.) We killed the final boss and he was able to keep progressing. I went back to town, still with only 2 amulets, and all the darkness in the city was gone and every NPC was congratulating me for lifting the darkness. I have waited over 30 minutes for Oak to respawn and he will not (I believe this is caused by me first choosing to help Oak.) I cannot go through the final door or TPs in the last area because I do not have the Apex.