Sandbox fantasy, cliche answer, I know. But this specific type allows you to merge different settings, make crossovers, and create interesting character dynamics. Two, or more characters from wildly different universes could make for some eye-catching interactions, maybe even give us a deeper insight into their traits and personality. Chiefly, it is a double-edged sword, capable of creating storylines that keep players on their toes, or absolute, orderless chaos where players run around like headless chickens. But it is a worthy gambit.