Stitched Pup!

When Gluth died to a band of brave adventurers, these lil' guys 

were found in the corpse, gnawing on giant, undead bones.

Gluth's Bone is a drop from Gluth in Naxxarmas that will 

teach the player to summon a Stitched Pup.

Grats to Askevar for getting the correct guess!