Uuna
Drops from The Many-Faced Devourer. Uuna was found bound to an Ur'zul, and was released into the Shadowlands, where she wandered in the utter darkness. Humanoid type. Wowhead guide: Warcraft Secrets guide: Join the WoW Secret Finding Discord to solve more puzzles, riddles and various mysteries the game has to offer.
Uuna is a secret ghost child companion pet obtained as a drop from The Many-Faced Devourer, a rare enemy in the Antoran Wastes that must be summoned using a bone effigy.
Guide awaiting review
Collect the Scroll
Loot the 
Call of the Devourer from mobs in the Scavenger's Boneyard, found at 55.5, 39.2 in Antoran Wastes. This scroll is required before the three bones will be visible to you.
Gather the Three Bones
Collect all three bones scattered across the Antoran Wastes: the 
Imp Bone at 65.6, 26.3, the 
Ur'zul Bone at 50.39, 56.15, and the 
Fiend Bone at 52.37, 35.33.
Combine the Bones
Combine the three bones together to create a bone effigy, then place it at the hill in Scavenger's Boneyard to summon The Many-Faced Devourer.
Defeat the Many-Faced Devourer
Kill The Many-Faced Devourer at 54.4, 39.2 in Antoran Wastes. Upon death, it has a chance to drop 
Uuna's Doll. The drop rate was increased via a hotfix on January 17, 2018.
Resummon and Farm Daily
After the first kill, you only need to place a new bone effigy each day to resummon The Many-Faced Devourer at 54.4, 39.2 — you do not need to recollect the scroll or bones again.
Tips
Completing Uuna's story questline after obtaining her unlocks access to the secret pet Baa'l and the item Waist of Time.
