theresa (arknights), theresis (arknights), arknights, artist request, official art, third-party source, 1boy, 1girl, armor, belt, breastplate, breasts, brother and sister, cape, closed mouth, cowboy shot, demon boy, demon girl, demon horns, dress, fur trim, gauntlets, greyscale, hair between eyes, horns, layered sleeves, long hair, long sleeves, looking at viewer, monochrome, own hands together, pointy ears, short hair, shoulder armor, siblings, very long hair, white dress