Dust Spirit
Drops from Docile Earthen Soul. When it was captured and bound to a cage made of enchanted metal, this spirit managed to twist and reshape the metal into the suit of armor it now ... Elemental type.
The 
Dust Spirit is a battle pet obtained by opening a 
Docile Earthen Soul, which is acquired by capturing an Earthshatter Elemental's soul in the Waking Shores during Dragonflight.
Guide awaiting review
Craft Required Soul-Capture Tools
You will need an 
Empty Soul Cage and a 
Zapthrottle Soul Inhaler before heading out. Both are crafted professions items — check the Auction House if you cannot craft them yourself.
Find Earthshatter Elementals
Head to the Crumbling Cliffs in the Waking Shores and locate the Earthshatter Elementals at 52.8, 30.6. These mobs can each be pulled individually without dragging additional enemies, making them ideal targets for soul capture.
Capture an Earthen Soul
Activate the Zapthrottle Soul Inhaler and begin damaging the Earthshatter Elemental — the elemental must die while the Soul Inhaler is actively channeling. Use damage-over-time effects and stuns to prevent the elemental from interrupting your cast. A successful capture places an 
Encaged Earthen Soul in your bags.
Wait for Soul to Turn Docile
Do not open the Encaged Earthen Soul immediately. Wait for the 15-minute timer to expire, at which point it will transform into a Docile Earthen Soul, which has a chance to contain the Dust Spirit.
Open Docile Earthen Soul
Open the Docile Earthen Soul — it will most commonly yield an 
Earthen Soul crafting reagent, but has a chance to award the Dust Spirit pet. Player reports range from 9 to 50 Docile Earthen Souls opened before receiving the Dust Spirit, so repeat the capture process as needed. The Dust Spirit is also tradeable, so it may be available on the Auction House.
Tips
One player received the Dust Spirit after 16 Docile Earthen Souls, while another took 50 — drop results vary significantly between players.
