He doesn't swim naked, so he takes the summon anyway.
Cam lays relays - after each sphere is safely exploded - and reports in on his progress regularly and updates his map.
Of course, they wouldn't have to evacuate their planet if they would talk to him, but aside from occasionally yelling at them about that Cam's fresh out of ideas.
Well, that's inconvenient. He'll have to go back and hunt down whoever did that and replace the relays and apologize for the interruption in service.
This looks like an unusually large Sphere.
Actually, it kind of looks like a planet.
Actually, it kind of looks like a familiar planet.
Also, once he gets clear of the giant crater where the complex housing the portal used to be, no one is shooting at him and nothing is blowing up. There are no more portals in sight.
"I found a planet. I found a real planet. I found the planet humans come from in my world. You don't have weird physics, you just have a weird magic system which allows pocket dimensions with weird physics. This planet looks perfectly normal if somewhat the worse for wear."
"Yep. And it's overrun by aliens. I will... wander around watching bits of the Earth self-destruct, I guess."
And Cam flies around, looking for aliens, possibly evacuating in something he'd like to get a tracking device on.
Cam lands.
Cam wonders vaguely how his program figured out "befoul", decides this is really not the time to go look at its inference backchain, and fumbles around with his vocabulary until he has his best approximation of "talk to me so I can talk to you".
Can he say 'I do not intend to kill you unless -'. Or 'you can live if you cooperate'. Or something.