Keeper of the Realm — H.J. Ralles

In 2540 AD, the peaceful realm of Karn, 300 feet below sea level, has been invaded by the evil Noxerans. This beautiful city has become a prison for the Karns who must obey Noxeran regulations or die at their hands. In the second thrilling adventure of the Keeper Series, Matt uncovers the secrets of the underwater world. He must rid the realm of the Noxerans and destroy the Keeper. But winning level two of his game, without obliterating Karn, looks to be an impossible task. Can Matt find the Keeper before it's too late for them all?