The 2017 film Kong: Skull Island first introduced the theory of a parallel world, often called Hollow Earth, in the MonsterVerse. As per the underlying theories, Hollow Earth is home to hundreds of MUTOs who inhabited Earth long before human civilization came into play. In the MonsterVerse, Skull Island acted as an area of refuge between the two worlds where both monsters and humans co-existed and lived in harmony. Kong, the king of Skull Island, became the savior of the tribals living there, who eventually started worshiping him as a god. The Apple Series, Monarch: Legacy of Monsters, shed further light into the Hollow Earth mystery, where we found out that it was Bill Randa who speculated the existence of massive underground spaces through which these Titans can move around the world without being seen. In theory, Gojira used the pockets between the two worlds to travel undetected; Kong and his ancestors, on the other hand, had been exiled from the Hollow Earth, which perhaps was the reason why he was clueless about the other realm. He and his ancestors spent the majority of their lives on Skull Island, and his lineage will be further explored in the 2024 film Godzilla x Kong: The New Empire.
After Shaw and Keiko’s disappearance in Monarch: Legacy of Monsters, Bill Randa was the only surviving member of the band who knew about the secrets of Hollow Earth. Or at least he was aware of its existence in theory. Therefore, in order to prove the existence of the Titan’s realm, Bill Randa assembled a team of soldiers and scientists soon after the Vietnam War and stepped on Skull Island in 1973. We are already aware of the things that Bill Randa saw on the isolated island, but what is important here is the fact that Bill died on the island. However, before losing his life to a Skullcrawler, Bill recorded a video of the island and its creatures and threw his bag into the ocean so the evidence could one day cross oceans and reach his son Hiroshi. Quite conveniently, it did, which marks the beginning of Monarch: Legacy of Monsters Season 1.
The first season of the Apple TV series implied that Hiroshi got hold of the videotape soon before the emergence of Gojira in 2014, as featured in the first Godzilla film in the MonsterVerse franchise, soon after which Hiroshi started his research for the Hollow Earth portals scattered around the globe. It is to be noted that the people at Monarch didn’t believe in Hiroshi’s theories about the Hollow Earth, which is why he didn’t have the means to visit Skull Island and instead traveled to more accessible locations like Alaska and Algeria.
When Lee Shaw first witnessed the portal in Alaska, he realized what Hiroshi had been looking for all these years. It was the reason why Shaw started tracing Hiroshi’s footmarks, which led to one portal after another. Shaw wanted to completely destroy these entry and exit points so as to stop the MUTOs from entering the human world.
Hiroshi, being a responsible father, wanted to keep his children away, but they fell straight into the dark pit, from which there was no coming back. Eventually, Cate and Kentaro became part of the family legacy, and Hiroshi failed to protect them from Monarch. While trying to stop Shaw, Cate fell into one of the Hollow Earth portals located at an abandoned Ukrainian nuclear plant in Kazakhstan, and Hiroshi blamed himself. However, at this juncture, Hiroshi believed in the possibility that Cate might not be dead, as he knew of his uncle Shaw, who had safely returned from one such portal. Therefore, after Kentaro’s insistence, Hiroshi joined hands with Apex Cybernetics and used their resources to predict the location of the exit portal from which Cate and others might emerge. Coincidentally, it turned out to be the same Skull Island from where it all began.
It could be speculated that Monarch was unaware of the existence of Skull Island for a long period of time. Hiroshi, on the other hand, revealed its location to Apex Cybernetics, who, being an independent body, was curiously looking for new avenues to explore. Their huge interest in MUTOs isn’t a surprise to anyone, which makes us believe that when Hiroshi informed them about Skull Island, they quickly packed all their gear and ended up on the island to explore its flora and fauna. However, Hiroshi was unaware of the fact that, in order to save his daughter, he had handed a nuclear weapon into the hands of those who might use it to destroy both worlds, and that was what actually happened.
So, the ending sequence of Monarch: Legacy of Monsters Season 1 confirms that Apex Cybernetics has already established its base on Skull Island. We are still unaware if Monarch knew about its operation or not. Cate and May had been away for two long years, and perhaps a lot of events took place in their absence. Apex Cybernetics started experimenting on Skullcrawlers and Kong, but they couldn’t take these Titans away from the island, as Gojira would sense their escape and attack as soon as they left the island. It is for this reason that Apex Cybernetics, in association with Monarch, constructed a huge dome called Kong Containment on Skull Island to tame the Titan, the Monarch outpost that was featured at the beginning of Godzilla vs. Kong. Additionally, Apex Cybernetics had smuggled the eggs of Skullcrawlers to train its most ambitious project, Mechagodzilla. Throughout the film, Apex Cybernetics was looking for a means to travel to Hollow Earth so that they could steal its energy source and power up their most deadly weapon, which makes us believe that their greed for powers hasn’t come to an end.
There might be hundreds of similar pursuits, which we will see in the upcoming season of Monarch: Legacy of Monsters. It is quite possible that after learning their true intentions, Hiroshi and Keiko will try to stop the evil organization from exploiting the Titans and the Hollow Earth resources. Or it could be possible that Hiroshi and Keiko will help these people develop transport vehicles that can easily travel between the two realms, therefore making Hollow Earth more accessible to human beings. But we are all aware of what might happen if the greedy humans stepped into Hollow Earth in huge numbers. They wouldn’t mind destroying its habitat like they destroyed theirs. If we think about it that way, it seems Shaw has been doing the right thing all along, trying to separate the two worlds. And yes, our beloved hero might return too to put an end to the Hollow Earth madness and finish the work that he had started.