The Moonlight World by Tunku Halim

"What do you do when strange things happen around you? The Midnight Children trilogy is a series of dark fantasy novels for children age 8-13 combining Asian mythology and Gothic elements. The characters, ten-year-old Min and twelve-year-old Zak are the main protagonists. In The Midnight Children- The Moonlight Lands, Zak by helping a ghostly girl at the hospital brings his mother out of a coma. In the meantime, Min is now Uncle Obb's prisoner in the Moonlight Lands. He has also become king of the oily creatures and wants to eat her, Zak and her father because of their inherent magic. King Obb leads his army across the desert to attack the Rising, an army of mostly children who are rebelling against the oily creatures. The Rising's man-horses raid King Obb's camp and Min is rescued. Meanwhile, King Obb sends Ragdoo, his Lord Chancellor, to kidnap Zak. Ragdoo betrays King Obb by taking Zak to the Moonlight Lands to defeat King Obb. King Obb's army of oily creatures attack the Rising who are hopelessly outnumbered. Just as Min and her father are about to be beheaded, Zak appears and, using their combined magic, they turn the tide of the bloody battle"--Publisher's description