Challenge Conquerors: Gold - Guild Edition

This guild achievement requires the completion of all nine Mists of Pandaria Challenge Mode dungeons with a rating of gold on each while in a group with at least three guild members. You do not need more than three guild members to participate in any given challenge mode to get "guild" credit for the run.

This achievement is going to become unobtainable in 6.0.2, so if you still need this pet, here is a list of guilds on various servers, both US and EU, who are willing to invite people just so that they can grind guild rep and obtain the [item=85513].

Edit: If you wish to obtain this pet, you can still get it from the Black Market Auction House, on the occasions when it is one of the random items posted there. Happy bidding!