Monsters are still trapped underground even though the barrier that formerly held them has crumbled away. Instead, a different magic keeps them captive a spell that sets the underground apart from the surface with no end in sight. A select few monsters managed to escape the magic due to their direct involvement with the CORE. The handful of monsters have begun to reach out to the now advanced humans for help freeing their kin with mixed results. After accidentally causing a human-rights issue on the surface and feeling they failed in their quest for help they returned to the CORE.
Now those on the surface face political turmoil now that they are aware of the sentient beings that were sealed away over a millennium ago. Some fight and raise money in an attempt to research and help the monsters while others want them annihilated for not being human. Most of the population does not care or does not believe the media about the monsters being a thing, content to think of it as a giant hoax.
Whatever you believe, they are calling out for help.