A Demoiselle "Knife" is shaped like a dragonfly. Its head and thorax are purple and its eyes are pink. Its long, segmented abdomen alternates between pink and white. It has four long wings, two on each side of its body. The tips of the wings are a very faint pink color, while the rest of them are white.
Demoiselle is French for "Damselfly", while its Japanese name, Libellule, is French for "Dragonfly".
These knives have the same combos as the Vol de Nuit. Both the ground and aerial combos are identical to the Foudre combos, minus the -combo. The -combo consists of Larxene leaping into the air and performing a vertical spin. After this, the player is prompted to press again, making Larxene perform her aerial finisher.