Leper Rat
Sold by Micro Zoox. The radiation from all of the machinery in Gnomeregan gives these rats a soft green glow when looked at in absolute darkness. Undead type. The is learnt from , which is purchased from Micro Zoox, who is just outside Gnomeregan.
The Leper Rat is a pet battle dungeon pet obtained by purchasing 
Leper Rat Tail from Micro Zoox outside Gnomeregan for 
3 Pristine Gizmo.
Guide awaiting review
Locate Micro Zoox vendor
Find Micro Zoox outside Gnomeregan in Dun Morogh. This vendor sells pet battle items including the Leper Rat Tail.
Earn Pristine Gizmo currency
Complete the Gnomeregan Pet Battle Dungeon Challenge to earn Pristine Gizmo. You can obtain one Pristine Gizmo per week, so you will need 3 weeks to gather enough currency for the Leper Rat Tail.
Purchase Leper Rat Tail
Trade 3 Pristine Gizmo to Micro Zoox for the Leper Rat Tail, then learn the pet from the item.
Tips
The Leper Rat Tail can be caged and traded on the Auction House, allowing you to purchase it from other players instead of farming Pristine Gizmo yourself.
