Shadow animals are animals transformed by energies from the Shadow Plane after having ventured into shadow-haunted regions despite their natural abhorrence of such places. Their colouration loses all brightness, and they gain a brutal cunning, to the point they can understand but not speak languages. Shadow predators are bestowed with unusual powers, and herbivores become more aggressive and dangerous than normal. On Golarion, shadow animals are most commonly found in Nidal.1
For additional resources, see the Meta page.