WoWDB

The item reward is the culmination of a long quest chain to "attune" the character to Black Temple (i.e.: be able to enter the raid instance). Attunement as a design philosophy was discarded during The Burning Crusade and removed from the game very late into TBC. The quests remain for purposes of lore, unique item goodies such as this medallion, and for achievements/reputation. The same used to be true of "vanilla" attunement quest chains until the Cataclysm expansion removed them as part of Azeroth's revamp.

Edit: Even as a mage, it was worth it to finish the quest just for Teleport: Black Temple. Quite handy. I also enjoyed learning parts of the story line that simply were not available to me back in TBC because I was not in a raiding guild nearly all of the expansion.