Turns things to ducks
Casting and effects
The caster will slash their wand downward to point at the target; a banana-yellow jet of light will shoot from the tip, with what appears to be a duck made entirely of brilliant yellow light soaring in front. When it hits the target, there is a burst of yellow light and when said light fades, the target is in the shape of a duck.
From English duck(ling) and fors (a suffix often used for transfiguration spells) from either the Latin meaning luck, chance" or the English "form".