Varga recognises the weapon as her own before it was stolen, but she’s happy for you to keep it and even happier to upgrade it for you. This time, she needs the snout of a Fire Bellowback. So, activate the errand from the quest menu and get going! You’ll be doing it alone this time as Varga returns to Longnotch to wait for your return.
Warning: You can access this part of the errand only when you have completed the Stone Yield bandit camp and defeated the Bandit Leader. You will receive the Forgefire weapon from the reward box.
Follow the trail to the Bellowback site (or fast travel if you prefer) to find a single Fire Bellowback stalking the hills with a Shell-Walker. Remember how Varga modified your Icerail to have explosives? Why don’t you try it out? Two explosives and a few arrows will be enough to burst the fire sac on its back – pretty impressive!
Finish it off and scavenge it for the Bellowback Snout. When you’re done here you can fast travel right back to Longnotch to speak with Varga again. She’ll upgrade the Forgefire, and then you can be on your way with your all-new and improved weapons!