Mini Spider Tank
From Pet Battle Challenge: Gnomeregan. Nobody is sure why someone thought making a miniature version of the machines in Gnomeregan was a good idea, but they sure are fun to play with. Mechanical type.
The 
Mini Spider Tank is a pet battle reward obtained by completing the Pet Battle Challenge: Gnomeregan achievement, which requires finishing the Challenge version of the Gnomeregan pet battle dungeon without healing your pets.
Guide awaiting review
Complete Challenge Gnomeregan
Enter the Gnomeregan pet battle dungeon and complete the Challenge version, which does not allow you to heal your pets throughout the run. Earning the Pet Battle Challenge: Gnomeregan achievement rewards the Mini Spider Tank.
Note the Ability Slots
The Mini Spider Tank's primary attack slot offers both U-238 Rounds and Batter, but these two abilities are mechanically identical — only differing in name, icon, and animation — so there is effectively no meaningful choice between them in that slot.
