The Zandalari Heritage Armor Set is an awesome-looking set that can only be used by Zandalari trolls. Getting it is pretty simply really, and it's awarded to all Zandalari trolls once they hit level 110. At this point it will be automatically added to your Wardrobe, and you can transmog it to any other item.
Once you unlock the Zandalari Heritage Armor Set, any Zandalari troll on your account can use it, even those that are below level 110. This means that if you see this on a low level Zandalari troll, it's a sure proof that they already have one Zandalari troll at level 110 +.
You will not get the Zandalari Heritage Armor Set if you buy a character boost, so you will need to manually level up your Zandalari troll if you want this amazing set.