These rares, discovered early in the PTR cycle, aren't your typical rare mob. Unlike the other rare spawns scattered around Pandaria, these are gold elite mobs that require far more skill. There are three different mobs that spawn -- stealthed scouts, flying elites shown in the picture above, and Zandalari Warbringers. It's the Warbringers that offer the most difficult challenge, requiring a tank and healer at bare minimum to bring down.
So where do you find these wonderful mobs, and why do you want to kill them?
But what about the sweet rewards? How about a mount for the taking? Each Warbringer is mounted on a Direhorn of a particular color -- and the Warbringers have a chance of dropping that Direhorn mount for you to ride. In addition to the mounts, there are a ton of other goodies available as well. Crafting materials are always nice, but far nicer are the Stolen Insignias from one of four Pandaren factions.
You can find Stolen Insignias for the Klaxxi, Golden Lotus, Shado-Pan and August Celestials. Each insignia will grant a whopping 1000 reputation to its respective faction. These Stolen Insignias are Bind-on-Account, meaning you can send them to an alt if you've already maxed out your reputation on your own time, which is a definite bonus for those with a stable of alts on their account.
Spend as much time as you'd like on the Isle of Thunder, there are certainly plenty of things to do. But if you're looking for a group-worthy challenge, keep your eyes peeled on Pandaria's shores. The Zandalari are waiting to take you on, and they'll reward you greatly if you pass muster and manage to bring them to an end.