User blog comment:ImperiexSeed/Supernatural Mysteries/@comment-3481504-20130307031256/@comment-5767263-20130307092548

Well, for one, who knows how big Heaven is. There may not be enough for them to chomp. For two, my guess would be Heaven, space, a different planet, or some other-but-easily-accessible dimensional plane. I would expect that the leviathans, being the indestructible, shapeshifting, sentient globs of goo that they are, could survive in a vacuum, since they would have no need of air or heat and even if they did (plus, they can levitate/fly under their own will, so the lack of gravity wouldn't be an issue), they could just regenerate, but the universe is a big, big domain and it doesn't seem like the leviathans would pose *that* big of a threat to it, considering that they'd potentially have to travel light-years between solar systems. So the the other three possibilities seem the most likely in my opinion. Maybe the even lived in a rudimentary "sub-level" of Heaven, like a basement. I'm not exactly sure why Heaven would have a basement, but it's really just a guess.