Sparrow is a weaponsmith, assassin and genius, she was originally born for a specific purpose, to kill Evill and Li, Sparrow was trained from birth for this specific purpose and was as such neglected in that part of her childhood, to the point where Sparrow had to name herself, she named herself after the first thing she saw when she decided she wanted a name... which was a sparrow... Sparrow was eventually sent out into the world to fulfill her purpose... Sparrow would go and to complete said goal, eventually... she would give up on it once she had discovered that the person she was meant to kill had suffered in the same way as her... Sparrow and Evill and Li were both adopted by a genius named River, and were raised... properly for the rest of their childhood... Sparrow now an adult, has learnt a lot from her foster mother, she owes most of her intelligence to her. Sparrow now works professionally as an assassin, she makes tiny portable death traps that she stores in her armour, her most prized creations are her crossbow and her armour, which are both technologically and magically advanced. Sparrow can fall asleep and wake up on command, and she is obsessed with sandwiches, they're her favourite food, She's best friends with a dragon named Key, one thing she always says is: "It's not that everyone else is stupid, it's just that I'm much smarter."

Sparrow lives in her own lab now. One she made for herself. In its own pocket dimension, similar to what River does with her lab.

Check the Writings, there's a better description there.

Sometimes Sparrow kills the people that hire her. But only if she doesn't like them enough.

Sparrow is also very silly.