Legends of the Ahvonians

Just days after the Battle of Terra Magon, the Stuart family is thrust back into danger after the Liberator is ransacked and wrecked by a mysterious new foe: The Nostrum Cult. Mortificus has sinister plans for everyone, human and Ahvonian alike. Only Marian and Wilbur are left behind, surviving the crash and detouring to the windy pastoral world of Aero Magon. There, they meet nomadic traders led by the Great Spirit of Wind, Tempestio. Only he isn't himself anymore.
Aenjiiv, the last Original Guardian, has taken Brian and Jennifer to the safety of his Sanctuary and teaching them his ways and methods. All the while, Mortala is bent on completing her master's mission: the integration of humanity into his nihilistic prophecy called the Restitution. She swore no rest until it is finished, despite some of her goals not going as planned.
Upon reuniting the entire crew with the help of the notorious rebel and smuggler Whintha-Deima, Marian rallies all to the dreaded supernatural storm Nimba-Norna: the Great Black Cloud. Fate turns wildly during the escape from the atmospheric maelstrom, restoring Tempestio to his former glory yet entwining Marian and Mortala through the Spirit Core of Darkness.
Suspense turns to horror as Marian realizes that Mortificus's plot was completely orchestrated, and she suffers gradually from the traumatic visions and corruption of her body. Whintha-Deima races against time to prevent the inevitable while miraculously stumbling upon the OMNI: The Orbital Maintenance Navigation Index. Just what does this ancient marvel hold for us all?