Carpal Pet

To create this pet, you need to combine the following three items:
Animated Ulna
Animated Radius
Flexing Phalanges

Animated Ulna Is the reward from the WQ Extra Pieces (Extra Pieces) (pet battle wq)

The Animated Radius is purchased for 250 Polished Pet Charms from the Undying Army Quartermaster, Nalcorn Talsen, he is found at Theater of Pain (or in Oribos)

Last thing needed is to loot Skeletal Hand Fragment In Maldraxxus for the Flexing Phalanges
This only works if you already have both Animated Ulna and Animated Radius; if you don’t, you won’t be able to interact with the object you need to loot to obtain the Flexing Phalanges.
Skeletal Hand Fragments is found in the Iron Trench region of Maldraxxus, just southwest of the Theater of Pain.
It’s located inside a huge skull located at /way 47.4, 62.1