Take characters from Tales of series: Symphonia, Destiny, Eternia, Rebirth, Legendia, and the Abyss, and place them all in a guild trying to ease the suffering of a town laboring under an evil villain. Oh, and there's a world-eating terror just outside the door. It's up to you, a custom-made character who can switch between jobs at will, to earn their trust and lend a hand.
The first entry in a crossover series of three PSP titles (a couple GBA games, and a tactical RPG on Android), Tales of the World: Radiant Mythology gives you the chance to unite heroes from several different canons, some of whom have better excuses for being there than others. There's a pile of quests to be done, respect to be earned, and a complex system of item creation to aid your tasks.