A Marked Flawless Battle-Stone is a consumable item added in Patch 5.3 that instantly upgrades a battle pet to Rare quality. Pets level 15 and greater lose up to two levels in the process. One marked flawless battle-stone is a reward from the Pet Battle achievement, The Longest Day. Marked flawless battle-stones can also be purchased from various vendors by trading in 3 battle-stones of a single type, or from Master Li in the Timeless Isle for 3 celestial coins.