Quite a peculiar pet, especially when it comes to getting it. Capturing the Armored Vaultbot requires the player to attack a rare elite mob and bring it to Bolten Springpsark in Bondo's Scrap Yard, where it will soon be sucked up by the Robot Cruncher.
The player must then loot the pile of treasure left behind, which can sometimes have a blueprint in it - Blueprint: Vaultbot Key - to create an Armored Vaultbot Key. The key must be used on the Armored Vaultbot, killing it in fire and causing it to drop a pet.