Sienna was born in the western mouse settlement of Sprucetuck, where mice pursue the sciences of medicine, harvest, pest control, and metallurgy. At a young age Sienna developed a fascination with the science of blending raw items together to improve their quality as finished goods.
Sienna joined the Mouse Guard and from 1142 served as a patrol leader. She spent much of her service leading groups between the northern settlements of the Territories. Sienna was adept at finding quick, safe and sure paths even in unknown wilds.