Zadar IV is a planet in the Zadar system. Zadar IV has large oceans filled with fish and other marine life. The planet is home to a human colony with a population of 6 million. The planet is also home to an Earthforce academy and a secret merpeople kingdom.
The kingdom was revealed when several young colonists met the princess of Atlantica, Ariel. The children began seeing each regularly, talking about their different civilizations. Eventually, the king of Atlantica found out and attacked the children, the princess was the only casualty. The princess was taken to a medical facility on the planet and revealed to John Gill. She then said she wished to live on the surface world with the colonists, Dr. Gill used a forbidden technology to help transform her into what she liked, as long as it was female. She chose the form of a human female. After eighteen months, the colonial government discovered the attack and decided to go to war with the Atlanticans. However, the younger colonists and the princesses intervened, the battle was quickly halted and both sides united to defeat a large monster. Eventually, the merpeople decided to relocate to an uninhabited planet, knowing that if they continued to live on Zadar, it would interfere with the colonists way of life. Some choose to stay behind, while others were relocated to the world of Gideon.