Pendragon series

Bobby Pendragon is a seemingly normal fourteen-year-old boy. But there is something very special about Bobby-- he is going to save the world. Bobby is slowly starting to realize that life in the cosmos isn't quite what he thought. Before he can object, he is swept off to an alternate dimension known as Denduron, a territory inhabited by strange beings, ruled by a magical tyrant, and plagued by dangerous revolution.

Bobby and the Traveler from Cloral--Spader--have flumed to New York City, 1937. Against a backdrop of gangsters, swing music, and the distant sound of a brewing war, the two must uncover the evil Saint Dane's newest plot

Just when 15-year-old Bobby Pendragon thinks he understands his purpose as a Traveler he is faced with an impossible choice

Quillan is a territory on the verge of destruction. The people have lost control of their own future and must struggle simply to survive. The only chance they have of finding a better life is by playing the Quillan Games. Hosted by a strange pair of game masters, Veego and LaBerge, the games are a mix of sport and combat. They use the people of Quillan as pawns for their amusement as they force them to enter competitions that range from physical battles,...

While Pendragon is trapped on Ibara, Alder returns to Denduron and reluctantly goes into battle again, and other Travelers face obstacles of various sorts, Saint Dane gains the power he seeks on Second Earth and makes his push to destroy and rebuild Halla