Kingdoms of Light — Alan Dean Foster

INSIDE THE RAINBOW!

Evil, sadistic (and badly socialized) goblins have destroyed the pastoral kingdom of the Gowdlands. Blasting the land's greatest wizard into cinders, they cursed it with a dark hex no mortal can break. But the mage's death unleashes a wondrous spell that transforms his pets--three cats, a dog, a snake, and a songbird--into champions with human forms, animal cunning, and magical talents. They'll need all their new abilities to save the Gowdlands. Because together the six must cross the Kingdoms of Light, realms where polychrome perils and multihued menaces await. For only they have the power to fight the coming of a black force that will annihilate all light... and all life.