Onyxien the Onyx Netherwing Drake

Yes you do need to be exalted with the Netherwing to be able to get a Nether Drake (in reply to Vcast and Kruzty).

Fortunately it is a lot easier than it used to be, at least in terms of player competition and time spent doing the dailies (all drop-dependant dailies like the Fel Glands and Netherwing Relic are 100% drops now). You do still need 5000g spent on your Epic Flying up front to be able to advance past neutral, but a regular flying mount will serve you just fine for the dailies themselves apart from the Dragonmaw Race questline.

Yes, you get a free Onyx Netherwing Drake. The only thing you need to pay for is 5,000 gold for the epic flying mount training.

There are six drakes to choose from; the quest text sounds rather ominous, but they just want to warn you that you only get one free drake, its color dependent upon which "[name] the Netherwing Drake" quest you choose. As long as you remain Exalted with the Netherwing, you can buy additional drakes for 200g each from Drake Dealer Hurlunk back at Netherwing Ledge. As andyy86 said, you must have 300 Riding skill, which costs 5,000g, to even progress beyond Neutral with the Netherwing. These drakes are sought after because they look cool, an