Dragon's Prophet and the promise of making a magical lizard your willing servant. But if you're looking for more details about the whole Smaug slavery deal, then a new dev post on the official site should clear things up.
Dragons come in many packages. First off, there are the three species in Dragon's Prophet: elder dragon, legendary dragon, and regular dragon. Only the last type are available to bond with, however. Dragons then come in four varieties: flying, aquatic, gliding, and land.
To snag a dragon of her own, a player has to engage in a capture minigame to charm a beast. If successful, then the dragon joins forces and can use one of its many skills in combat. Dragons can also give players special skills as well. When players aren't using dragons, they can put them in a dragon lair or assign them to tasks such as gathering materials.