I rather like this dragon. I had a lot of vague thoughts about their society and history. I’m not sure what world they live in, what other dragons or non-draconic races they coexist with (or are tolerated by), and so on, but I’m pretty sure that they eat stone, notably defensive structures (like your castle), to help maintain bone and horn density. They definitely breathe fire.
Probably chafes something awful,though, but I figure they bear it with pride.