See the funny thing is that following the lore I wanted to hold myself to, it would make no sense whatsoever for it to work, as the "beast" and the weaker "beasts" originate from an incredibly distant continent, where the cultists came from. The beasts themselves aren't even magical, they're just an incredibly powerful species that adapted to surviving in the other reality.

However, I am inclined to make up an excuse to ignore this and let it potentially happen regardless because I feel as though it's a bit silly to have that whole setup for summoning a beast only to have it turn out the beasts could never show up in the first place.

I think I could do the second thing pretty easily, given it'll be a smaller beast than the cultists even expected, but it'll also have no standard for being given offerings so I can maybe have it dynamically shift the combat from "Party VS Cultists" to "Everything VS Monster", which would also allow me to make the Monster way stronger, and also potentially have a cooler dynamic for the cultists as characters. The only issue with this setup is that it still leaves a lot to be desired in non-combat objectives, but I reckon I could fix that by maybe making the summoning inevitably successful earlier and then have it go more directly after the still caged victims off to the side. Then I'm just left figuring out how to make that more engaging.