From Tokyopop:
Nightmares are bad enough when asleep, but In Dream World, nightmares are real, physical monsters!
Drake, Hanee, and Kyle fight these Nightmares with not only weapons, but "In Dream Cards". These cards have different elemental powers, and those who wield the cards are masters of their elements. Hanee and her friends must battle their way through the land of Nightmares to find their way home.