I need some synonyms

[classicdrogn]

I don't have any more to add as such, but I call your attention to a famous piece of writing advice: just call a door a door. Once you've described it in detail once, the reader is not going to want to focus on it every time your character uses one, any more than they want to spend time reading about how a science fiction character taps a glowing button on the wall to activate a dozen curved leaves arranged like the iris of a camera to retract out of the ovoid frame before stepping through more than the first time. In this case, just call a portal a portal - it's not like it's any more foreign as a concept to most modern audiences thanks to D&D, Stargate, decades of comics, and countless video games, including the eponymous Portal series itself.