Bone Serpent
Drops from Traveler's Pet Supplies. Young bone serpents will try to burrow into a living creature's skull and devour their brain. So you may want to wear a night cap. Undead type. I always wanted a mini pet! (However, I wanted it is a hunter pet.) Not that I mind settling for this one, for now.
The 
Bone Serpent is an undead wild pet from the Warlords of Draenor expansion, obtainable as a possible drop from a 
Traveler's Pet Supplies bag earned by battling Garrison visitor pet tamers Erris the Collector or Kura Thunderhoof.
Guide awaiting review
Locate a Garrison Tamer
Wait for either Erris the Collector or Kura Thunderhoof to appear as a visitor at your Garrison. These are pet battle NPCs whose defeat rewards a Traveler's Pet Supplies bag.
Defeat the Tamer
Complete the pet battle against Erris the Collector or Kura Thunderhoof to receive the Traveler's Pet Supplies bag, which has a chance to contain the Bone Serpent pet.
Tips
The Bone Serpent is notable for being the first non-flying pet to have access to Nocturnal Strike, and its Move and In abilities were moved into the same slot in Battle for Azeroth, so you cannot use both together on a single pet — fielding more than one Bone Serpent on a team works around this limitation.
