Inferno is the castle smith and armorer. She provides the guards with all their weapons and armor. She was a unicorn born to a family of earth ponies, so she was viewed as an outsider. Her father was a smith, so she had plenty of time to learn the trade. She moved to Canterlot and got hired as the castle smith.

She is only a side character because she'll only be around for the first few chapters, whereas the others will be there the entire story. Her cutie mark actually got imported successfully, so .