The Sun Sword Trilogy Series by Belinda Murrell

Ethan, Lily, Saxon and Roana have cracked the code, only to find that the Moon Pearl is being sent by ship to the land of the invaders. The four children must give chase to save the precious stone! The fisherfolk can help. So can Saxon's mysterious acquaintance, Fox, a smuggler who will do anything for a pouch full of Roana's gold. But the sea is far more dangerous than the land. There are sea monsters and wild storms - not to mention the deadly warship they are chasing... moreEthan, Lily, Saxon and Roana have cracked the code, only to find that the Moon Pearl is being sent by ship to the land of the invaders. The four children must give chase to save the precious stone! The fisherfolk can help. So can Saxon's mysterious acquaintance, Fox, a smuggler who will do anything for a pouch full of Roana's gold. But the sea is far more dangerous than the land. There are sea monsters and wild storms - not to mention the deadly warship they are chasing. Will Fox's stealthy black sloop, the Owl, carry them to safety, or will the Moon Pearl remain in the hands of their enemy? less

The adventure is far from over as Ethan, Lily, Saxon, and Roana ride for the snowy mountains to rescue a prince—and save the kingdomEven with the Sun Gem and the Moon Pearl safely sewn into the hem of Roana's cloak, the quest is far from over. Lord Lazlac is planning to marry Queen Ashana to secure his rule of Tiregian, and the queen cannot escape or rebel against him—not when her young son, Caspar, is being held captive by Sedah priests in the snow-covered mountains to the north... moreThe adventure is far from over as Ethan, Lily, Saxon, and Roana ride for the snowy mountains to rescue a prince—and save the kingdomEven with the Sun Gem and the Moon Pearl safely sewn into the hem of Roana's cloak, the quest is far from over. Lord Lazlac is planning to marry Queen Ashana to secure his rule of Tiregian, and the queen cannot escape or rebel against him—not when her young son, Caspar, is being held captive by Sedah priests in the snow-covered mountains to the north. It is up to Ethan, Lily, Saxon, and Roana to travel deep into the mountains to find Roana's brother before it is too late. But have they forgotten about the uncanny tracking abilities of the persistent Sniffer, who would stop at nothing to find his prey? less