A portal to another world opens in front of you....

[Heroine of the Dragon]

You don't know how long it will stay open or if you'll be able to get back if you go through. What do you do?

[CaptHayfever]

I try to find somebody who can figure out how long it will stay open & if I'll be able to get back.

And remember, "I'm-a Luigi, number one!"

[Deku Tree]

Probably try to send my phone in as a probe. On a string if I can manage it, in case there's a chance to pull it back once I've seen what I'm going to see. Live stream broadcast it to social media so there's a recording available even if I don't get it back. Could be that it would lose signal as soon as the phone went through, though.

[I REALLY HATE POKEMON!]

Might be dangerous. Probably pass unless I could determine its safety.