[For a moment, Vexen turns his interest to the TARDIS instead of Ten, scrutinizing what he can see of it. It doesn't look like any sort of typical ship.....]

That's generally what people use to travel between worlds, I'm told. If your craft is capable of navigating through time at will as well, then it's no doubt significantly more advanced than any Gummi Ship I've ever heard of. How exactly does your TARDIS accomplish such travels?