Iron Boot Flask
Source: Vendor. Mounting breaks the effect.
The 
Iron Boot Flask is a reusable toy obtained from a vendor in the Storm Peaks during the Wrath of the Lich King expansion that transforms you into an Iron Dwarf.
Guide awaiting review
Farm Relics of Ulduar
Travel to the Storm Peaks and kill Iron Dwarf mobs, golems, and Iron Gnomes until you have collected 20 
Relics of Ulduar — 10 are needed to complete a quest that unlocks the vendor, and another 10 are required to purchase the Iron Boot Flask itself.
Buy the Flask
Turn in 10 Relics of Ulduar to complete the quest and convert the NPC into a vendor, then spend the remaining 10 Relics of Ulduar to purchase the Iron Boot Flask. The item has unlimited charges and a 1-hour cooldown.
Tips
You can activate the flask while already mounted to appear as an Iron Dwarf on your mount, but once you dismount you cannot remount while the transformation is active.
Players without Wrath of the Lich King installed will see a blue and white square icon instead of the flask's proper icon.
For a visual walkthrough, see the video guides linked for this item.
