Magic Limitations

Only two types of magic are wholly off-limits: long-duration flight, and long-duration planar travel.
The nature of the elemental planes that feed energy into the world makes it impossible for magic to create permanent flight. Powers that grant flight for never last more than five minutes, though flight with wings is fine, as long as the creature is Medium sized or smaller. There are no flying carpets or airships. Since the reported extinction of dragons, flying creatures do not grow any larger than an eagle or condor.
Likewise, despite theories that suggest it should be possible to travel to distant planets via mighty rituals, all attempts to visit any foreign world never last longer than a few rounds before the traveler is shunted back to this plane. It is possible to wander into the Dreaming or the Bleak Gate and return, but even these trips are usually only possible when the moon and stars align properly, and getting back can be even more difficult than going in the first place.
Mechanically, this means that no creature can ever leave its home plane for more than five minutes, barring unique circumstances that are beyond the control of player characters. Such options may become available to PCs later in the campaign, but traveling to another world in Zeitgeist is never as simple as casting a single spell.