As a quick and effective spell usable against animals, this effect might have a chance to have a decent Penetration against a magical beast.
Leg of the Newborn Lamb
Muto Animal 15, R: Voice, D: Diameter, T: Part
Momentarily Shrinks an animal’s limb to the size of a newborn. A stress roll of Dexterity + Athletics vs. a difficulty of 12 must be made to stay upright if the animal is moving quickly or in combat. As T: Part is used the overall size of the best is less of a consideration for large animals.
(Base 3 to change an animal limb, +2 Voice, +1 Diameter, +1 Part)