Caustic

Caustic grew up alone and isolated. The only survivor of his clutch. From his first days as a wyrmling, he knew a deep unending need to devour as much metal as he could. He was attracted to the deep parts of the world and for a time managed to get his fill in the tunnels beneath the Maytara Mountains. As he grew his presence became increasingly intolerable for the Gieldur dwarves that lived nearby. Eventually, a band of dwarfs were sent to drive the now-adolescent wyrm from their home.
Outraged by the actions of the dwarfs Caustic developed a deep mistrust of others. He would often engage in open conversation with them but only so he could glean what information he wanted, convince others to do his bidding or just to toy with their minds. He would often conscript humans into providing him with heaps of scrap metal and armour to devour. Do this or have your homes destroyed. Outright threats were seen as pathetic by the dragon. Instead, he preferred to convince others that it was in their interest to have the dragon there via means of deception with any threat only implied.
After some years of wandering relying on humans and other creatures to provide him with food, he finally found what he'd been looking for. A relatively untapped reserve of iron in the village of Gloomsbreak. He took up permanent residence there burrowing a lair beneath the ground. He gorged himself on the reserves until all the villagers left as their livelihood had been stolen and found a copper mine to the south-east in what became Immesvale.
Now, many years later Caustic is a fully grown rust dragon that some say still resides in the mines beneath Gloomsbreak.