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I basically have a mechanic in my universe that allows humans to travel to different worlds (called offworlds) filled with different creatures and systems of magic, and this is very integral to the plot of the story. Currently I have things set up in such a way that humans are allowed to go to these worlds, but not vice versa because the human world and system of magic present within it acts as a "veil" making it undetectable by outside worlds and magical systems. My only concern is that this seems a bit conflicting with the fact that while humans can go to these worlds....they can also come back.

My current idea to explain this is that they use a combination of magic and technology to make "gates" which allow them to link themselves to them using a device they carry with them to these other worlds. Basically the device maintains connection to the gate and (for lack of a better word) "yanks" people back to the gate when activated in most circumstances. Is this a good enough justification for a workaround to a system which is otherwise impervious to outside magical forces, or is there more details I should look to add in the general sense to make it seem less gimmicky?

I think that two simple rules could provide a mechanism for this:

Rule 1: You are a part of the world you originate from, and you can always let yourself be pulled back there.

Rule 2: Earth is 'veiled', and cannot be discovered or located from the outside.

This way, even though people from Earth who travel to a different world cannot locate it from outside, they are innately able to let themselves be transported back there due to the affinity every being has for their homeworld.

Another possibility is that the Earth is "odd" compared to the rest of the worlds in the multiverse. It doesn't fit into any understanding that outsiders have for the shape of the wider multiverse, so they have never noticed it before. This would be less a case that they can't go there, and more that they just haven't so far. Could be narratively interesting then if human exploration of other worlds tips off the outsiders that there's another world to find.

Earth can be veiled, but the humans already KNOW where it is, so they can magically access Earth just like any other world. It's like they know a secret combination, or the coordinates of something that appears invisible.

Think of it like Star Trek's Transporter system. They would never transport themselves into solid rock, but if they know there is a secret room under all that rock and its exact coordinates, they can beam into it. (Apparently beaming into solid air is not as big a problem as beaming into solid rock.)

Your system is the same; nobody off-world risks transporting themselves into empty space, it is lethal. And space is too big to explore that way, even if you could survive for a second before transporting back. But the humans know the incantation, or combination, or thought-image, or whatever you want to call it, for getting to Earth.

Then you don't need a device or gimmick or anything else, you hardly even have to explain this. A thought-image of where you want to be might work well, a mental image is not the kind of thing that can be extracted by torture. (But maybe by magic.)