Perfect Deviate Scale is a better than average scale from the mutated deviate creatures in the Wailing Caverns. Perfect Deviate Scales are only used in one Leatherworking recipe which is a reward choice for Deviate Eradication from the Wailing Caverns quest giver Ebru in the cave above the Caverns, but the recipe is a superb one, and the individual scales sell for gold in the auction house.