Is part of the meta achivement needed for Loremaster of Outland.
It has different demands depending on wether you play Horde or Alliance.
Horde has to complete at least 87 quests in Nagrand.
Alliance has to complete at least 75 quests in Nagrand.
To help you get on your way here is a link for Nagrand questing guide.
Remember that some quests leads to Nagrand from other areas of Outland.