Memory:Giant rust monster

Like their lesser brothers, giant rust monsters were trapped in the Drakalor Chain against their will. These huge creatures suffer a lot from the inadequacy of their new environment. As they never seem to find enough minerals and metals to keep themselves fed, they are constantly in a very bad mood and attack everything that moves. At some point in the past giant rust monsters seem to have undergone a magical transformation of some kind. They are a lot stronger and more cunning compared to the various lesser rust monsters. Additionally they sport four tentacles (instead of the usual two) on their head, which rust everything they manage to touch. You could sense this creature through half the dungeon, simply by the way your polished metal equipment slowly seems to tarnish and corrode even as you near it. It needs a lot of metal to support its bulk, and perceives you as a large heap of food with some insignificant meat strewn in.