Despite the name, Mycea does not home mushrooms, rather large amounts of iron and silver. The mountain is a volcano. The fire giants mine said iron and craft extraordinary weapons and armour. Disasters strikes, from the deep caverns of a long-forgotten mine, abandoned since it was depleted of its resources, swarms of rust monsters surface, eating the giants precious metal, the giants fought the insects back into the caverns and fortified the gates. I need help with a reason why they can't simply walk in without any metal and stomp the critters to death and eradicate the swarms. What creature makes sense to be paired with rust monsters? I like the idea of a part of the mine being shut down because of a flood in that area, and then creatures could hop into the warm waters where they lay eggs and do insect stuff. Basically, I need something stopping the giants, atm they're (the giants) waiting to gather a "strike force" of magic users to handle the issue. What are some ideas?