Saint Dane wants to destroy the kingdom and bring in a new evil rule, the only one standing in his way is Bobby. So far Bobby has done well with his powers but another kingdom needs his help now. Plague has reached the domains of Eelong and they have no cure for this evil. Bobby knows about the cure thus he can save the kingdom. For this first, he has to go to another kingdom from where he would be able to get the cure, and then he can go Along with the cure.
The thing is easy to say but fulfilling the goal is not easy because Traveller cannot transport different things from one kingdom to another. If Bobby does such an act then it means that he would be defying the laws of the land. Such an act will endanger his life and the life of the people he holds dear.