There is but one known example where the world is referred to as the World of Serenia, and this appears to be a rare useage. Usually the entire world is known as Earth or World of Daventry. More accurately the World of Serenia appears to apply to a slightly different parallel universe of Serenia (see the events of King's Quest V (NES)).
Graham on his journey encountered the Desert Temple, the Crystal Caves, and the Forbidden Forest The. continents of the world are laced with crystal caves, forbidden forests, bandit hideouts and treacherous seas filled with mystery.
When his adventure begins, Cedric leads Graham to the land of Serenia to meet his kind master Crispin. Beginning from Crispin's house, Graham and Cedric journey far in their efforts to save the royal family. Aided by the know-it-all owl Cedric, and with the powers granted to him by Crispin, Graham made his way across the countryside of Serenia. His journey took him to the barren desert to the west, and across the treacherous mountains to the northeast. On the other side of the mountains he crossed the sea and found the island stronghold of the evil Mordack.