The Sunken Kingdom Series by Kim Wilkins, D.M. Cornish

EVER SINCE EMPEROR Flood drowned their kingdom and overthrew their parents, Asa and Rollo have been hiding out in Two Hills Keep. Then a mysterious stranger tells them their baby sister wasn’t killed along with their mother and father. Instead, she was kidnapped by Flood’s half-sister and secreted away in a castle to the north. If Una is still alive, there’s only one thing for Asa and Rollo to do... moreEVER SINCE EMPEROR Flood drowned their kingdom and overthrew their parents, Asa and Rollo have been hiding out in Two Hills Keep. Then a mysterious stranger tells them their baby sister wasn’t killed along with their mother and father. Instead, she was kidnapped by Flood’s half-sister and secreted away in a castle to the north. If Una is still alive, there’s only one thing for Asa and Rollo to do. They must take Northseeker, an invisible ship built of mist and shadows, and cross the danger-filled sunken kingdom. less

AFTER RESCUING UNA from the witch princess, Asa and Rollo are once again safe in Two Hills Keep. Asa is curious about the Moonstone Star and its magic, which she inherited when her mother was murdered. But when Asa tries her hand at her first spell, a band of underwater pirates called Tide Stealers appears and steals the jewel away! In order to get it back, Asa and Rollo must face malevolent ghosts, nasty sea giants, and one particular Tide Stealer who may hold secrets about their past.

FOR OVER A year, Asa and Rollo have believed that their parents were dead. Then they overhear a conversation between their aunt and their friend, Skalti, and they aren’t so sure anymore. A sorcerer named Ragni may know what happened to their parents, but Ragni is Flood’s prisoner. Asa and Rollo set off on a dangerous trip to question the sorcerer. Nothing will stop them from finding out the truth about their parents!

AN EXPLOSION WAKES Asa and Rollo in the middle of the night. It’s their enemy, the evil emperor Flood, destroying the homes of innocent people in his search for the two royal children! In order to protect the people around them, Asa and Rollo know they must leave and search out the man they have been avoiding all along. They sail the invisible ship Northseeker to Flood’s stronghold, Castle Crag. If they are lucky, they will find their mother and father in the castle’s dungeons... moreAN EXPLOSION WAKES Asa and Rollo in the middle of the night. It’s their enemy, the evil emperor Flood, destroying the homes of innocent people in his search for the two royal children! In order to protect the people around them, Asa and Rollo know they must leave and search out the man they have been avoiding all along. They sail the invisible ship Northseeker to Flood’s stronghold, Castle Crag. If they are lucky, they will find their mother and father in the castle’s dungeons. But one thing they know for sure—it’s time for a final showdown with Flood! less