"So," says Bella to Rúmil one afternoon, "a few weeks ago I told myself that if in a few weeks I had not come up with an actually good way to bring up a thing I would just mention it anyway on the grounds that if it came up somehow later and I had not done so that would be weird."
Well, as long as the demons weren't coming into contact with any non-Elves that might be all right.
Not at the point of contact, but better safe than sorry.
Aren't there nonhuman nonElf species in their world?
Orcs are like Elves that way; Dwarves don't seem to have souls, they haven't gagged any demons and none have asked about their souls. There are a couple newly imported species (it's a long story; their stars got extinguished so the Noldor relocated them really fast and now they're in summoning range) but no reason any of them would be visiting a prison planet.
Still, maybe just a no talking to nonElves binding.
"Maybe, but the more and the more openly we act there the more likely the multiverse stuff gets widely known. Highest leverage intervention is probably publicizing Limbo, but it'd just lead to more questions and now that anyone knows you can come and go..."
"Yeah - and Limbo's nice enough now that we needn't be strongly motivated to prevent people from ending up there - I'm surprised it has stayed secret this long but there are probably better priorities than figuring out how to change that."
"Yeah. Compared to most places Revelation's great."
"Congratulations on that." And they turn their energies to places of greater concern.
Loki's frost giants get assigned to run a refugee camp on this constantly-raining world where twelve million people got displaced by an ongoing war and their neighbors are all professing great concern for taking them in once it's demonstrated they aren't going to spy for the other side. The place has magic - people can freeze raindrops in place - which is mostly useless but of religious significance such that the refugees decline to be evacuated elsewhere.
The frost giants are... not Elves... but they can do their jobs and respond well to command structure.
"What's so great about you?" wonders a frost giant, who is idly trying to duplicate the raindrop trick with ice.
"Well, if you put it like that we've only had the one war and it was Asgard's fault."
"Asgard decided it'd be aesthetic if in addition to their own planet they had these eight other paraphysically neighboring planets too, as protectorates. They were inhabited."
"Some of 'em still haven't even been notified. Some of 'em went to war. We at least didn't lose outright. Princess Beldri's adoptive father was a captive given to the Asgardian queen as tribute."
Elves have been doing this for long enough that they manage not to all go incoherent with horror.
"I think," someone ventures, "there are some kinds of people who will be as bad as they can get away with and some who will be exactly as decent as expected of them but not a bit more and then some people who, you know, wouldn't do that even if everyone thought it'd be glorious, and Elves mostly don't have the first kind and have high expectations for the second kind and have our fair share of the third."
"Asgardians think all kinds of things are glorious," says the frost giant.