First is the Luciendar, which you probably already know is "the fabled weapon used to defeat the mighty desert dragon Tang'Raoul." Basically, it's a giant, super-powerful, two-handed sword that you'll be able to access once your character reaches level 15. Second is "the Labyrinth," an exclusive bonus area with its own set of quests that publisher SouthPeak has detailed to a hyper-nerdy extent after the break.
SouthPeak's description of the Labyrinth pre-order bonus content:
"The deadly Labyrinths of Hatmandor have become infamous throughout the lands of Antaloor. Countless adventurers have journeyed into the depths only to be lost of the shadows of the crypts. The Labyrinths were built ages ago to serve as the tombs of ten of the most powerful priests who lived in the Hatmandor Temple. Buried deep beneath the desert sands, the builders erected small underground pyramids to house the sarcophagi, and created an elaborate network of twisted tunnels to protect the tombs from grave robbers. Recently however scholars of the New Ashos University appear to have discovered remnants of the Labyrinths floor plans! It is said however that those who may manage to find their way through the convoluted mazes of the Labyrinth to the rewards within will have to face the decaying priests themselves in order to claim their treasures.
"Seize the unique opportunity to explore the intricate Labyrinths of Hatmandor. Plunge ahead into the dank crypts of the temple priests in search of exquisite treasures, but be prepared to have your skill tested as the quest will not be an easy one."