Well, seems you two are the only ones here, but I can work with that. Come on.
*Before Sam enters the portal Sam activates one of his claws and etches "All who are interested, enter the portal behind the sign. Join at any time." into the sign. He then motions for Eito and Leo to enter the portal after him. Through the portal is a giant metal chamber with windows around the top of the walls. In a controls booth at the end of the room, Mayu sits, looking over some screens. She looks up and waves at the group as they enter. Looming overhead is a giant, mechanical puppet. Sam walks to the back of the room.*
I'm going to set up. Mayu, explain it.
Mayu (Comms): On it Boss. Time for Mayu Explains All!!! See, the Boss is trying to weaponize the portal network past opening it up for Marion to attack. So, he's going to drag things from other worlds into fight you guys. Your opponent will be the Boss and anything else he brings in. Due to a shieldy thing he has on his arm, you'll have to kill the things summoned first, I think it was. I'll keep track of your vitals to make sure none of you drops dead. So. Any questions?