Just as a heads up for those still seeking the Thundering Serpent Hatchling
, this pet might only
be available on the BMAH in WoD. It's currently not listed as a guild reward on the beta (only the new Draenor Challenge Mode unlockable pet is listed).
It's possible that the serpent hatchling could still be available from a guild vendor, and it was merely an oversight that it wasn't added to the rewards tab. Or it really could become a BMAH exclusive pet. Until we get some official confirmation, all we can go by is the Pet Journal and firsthand experience.
I've no clue how much it will cost on the BMAH, but it will most likely be more than 300 gold.