Fourteen-year-old cousins Gwen and Vic have lived together ever since the mysterious deaths of Gwen's parents and the disappearance of Vic's mother. But Vic's scientist father accidentally transports them through a magical crystal door to the island of Elantya. Cobblestone streets and silver towers mark the picturesque island, a trading hub and center of knowledge that runs on advanced physics and sorcery.

Vic and Gwen are soon caught in a tempest of ancient magic, vicious creatures, fierce battles, and a territorial feud with the sea-dwelling Merlons.

Gwen and Vic are still celebrating their victory in the battle with the Merlons when they learn that Vic's father has finally made it through the crystal doors to the magical island of Elantya. But their victory is short-lived when they and their friends are kidnapped by their underwater enemies and taken beneath the sea. There, they learn of a scheme that could bring Elantya to ruins.

Can they escape in time to save the island from destruction?

The thrilling conclusion to the Crystal Door's trilogy finds cousins Gwen and Vic and their three friends forging the magical Ring of Might and defending all the worlds beyond the crystal doors in their final battle against the dark sage, Azric. When their friend Sharif is called back home by his father, the Sultan, Gwen, Vic and their companions travel to the flying city of Irrakesh only to find that the Sultan is dying, with Sharif the next in line to the throne.Before he can choose between duty and destiny, Irrakesh is attacked and the city is taken hostage by the dark wizard's monstrous winged army. In their previous battles, the companions faced Azric by land and sea; now they take to the skies for the climactic showdown with the evil wizard and all of his dark forces.

Poisonous jellyfish and deadly stonefish attack Hawaiian beaches. Whales enlarge the assault against human sea activities by blockading naval installations and shipping lanes. Kimo Pohaku, a young Hawaiian man covered with tattoos of marine animals, emerges as the leader of this war from the sea, declaring war on humanity. Kimo may look human, but he has been transformed into something else, something dangerous.

In the ocean’s war against the humans who have caused so much damage, Kimo Pohaku leads a corps of transformed hybrids who are part human and part sea creature. Calling themselves the Sea Warriors, they can command dangerous aquatic creatures against human activities in Hawaiian waters, creating a massive strike back against human abuses in the ocean. But when the government takes violent reaction against the demonstrations, the confrontation escalates into war.

Kimo Pohaku and his Sea Warriors have declared war against human civilization, because of the severe environmental damage humanity has inflicted on the ocean and its life forms. Leading a powerful armada of sea creatures against naval forces, Kimo has set a high goal: The complete liberation of the seas from human control, and preventing mankind from using the waters again for selfish, destructive purposes.