Helen

Helen, emphasis on the first three letters, is your dragon. Her real name is something you can't even begin to pronounce, since it's in her native language. She allows the nickname because she gave up on trying to teach you her real name. She speaks English, but she has to really think about the words before she says them. She isn't a social creature, and the only times she comes into contact with another being is when she's mauling them in bloody battles. She's very combat oriented, and that trait fits her perfectly because her body is highly optimized for flights as well. Razors for teeth and claws, powerful wings, thick scales, and a slim body. The cherry on top is her back, where spikes run along her spine, which ensures that she must be fully compliant for anyone to be on her and live. You are in the military, fighting a small battle against some smugglers. Helen is doing most of the damage.