Varga isn’t exactly impressed by the design of the Icerail weapon – she wants to improve it, and to do that she needs a Thunderjaw Mandible. Of course, she wants to go with you again to help. Equip the errand from the quest menu and check the map for the Thunderjaw site – you may only be able to fast travel so far before making the rest of the trip on foot.
Warning: You can access this part of the errand only when you have completed the For the Werak quest line and have received the Icerail weapon from the reward box.
When you arrive at the site, follow the waypoint to speak to Varga who’s waiting on a cliff as she looks down on the Thunderjaw. Initiate the fight when you’re ready, and once you’ve successfully taken down this huge machine, loot it for the Thunderjaw Mandible and return to Varga.
This time, she’ll take the Icerail weapon and modify it so that it can shoot Freeze explosives! These will come in handy for your next errand with her. Choose Forgefire from the dialogue wheel to start it up.