"Guardian! Where have you been? I thought the King sent out a distress call when paranormal activity was observed in the Crypt. Now, look at us. If you had come sooner, perhaps CluDathoon would have been more reluctant to attack. Nevertheless, here we are. You know, I never fully trusted Lax. I don't know why we let him into the Marketplace in the first place; he always seemed unstable to me. When CluDathoon attacked, Lax turned on us, and actually tried to prevent us from escaping. Last I heard, he had taken up shelter in the old Witch Lair, southeast of Avalon and right beside where CluDathoon launched the Camlann device. I think we'd all be better off if something 'unfortunate' happened to him. Go to the old Witch Lair, and kill Lax."
This is the first of the quests you will receive from members of the Resistance for the rest of Chapter 4. Leave Resistance HQ and head to the left, following your compass to the Witch's Lair. When you have located it, head down the spiral staircase and find Lax. When you have killed Lax, return to Resistance HQ. Speak with Festus for the next quest.