Godzilla vs Kong has revealed why Godzilla: King of the Monsters' post-credits scene was so important. After the epic battle for Titan supremacy between Godzilla, Rhodan, Mothra, Ghidorah, and all the rest, it seemed that Godzilla had successfully eradicated all traces of Ghidorah's alien body from existence, using his nuclear mode attack. However, the post-credits scene revealed that was not entirely the case: eco-terrorist leader Alan Jonah (Charles Dance) managed to procure a crucial item: the severed left head of Ghidorah, which had been lost in the oceans of Mexico after Godzilla struck a divisive blow against his alien rival.
The question that Godzilla: King of Monsters left fans with was: what kind of trouble could Alan Jonah cause with the head of Ghidorah? A lot of fans figured it was some kind of scheme that would lead to Ghidorah's resurrection - but that theory was very wrong.
Warning: Godzilla vs Kong SPOILERS Follow!
As it turns out, Ghidorah's severed head wasn't the key to creating new Titans - it's the veritable source code for an unholy creation: Mechagodzilla.
One segment of Godzilla vs Kong's human story follows Bernie Hayes (Brian Tyree Henry), a former technician at Apex Cybernetics. After the death of his wife during a Titan attack, Bernie went a little nuts and started a conspiracy theory podcast to expose the truth of what Apex is working on. That investigation roped in Madison Russell (Millie Bobby Brown) and her friend Josh Valentine (Julian Dennison), who ended traveling with Bernie to Hong Kong, to Apex's base there, where they make a startling discovery: Apex has built a Mechagodzilla that is operated by a cybernetic neural relay. The key to creating that cybernetic relay? The severed head of Ghidorah!
The relay was created by Ren Serizawa (Shun Oguri), the son of late Monarch scientist Ishiro Serizawa (Ken Watanabe), who is one of Apex's chief scientists and tech engineers. While the relay allowed Ren to control Mechagodzilla, there was insufficient power to keep it running. Apex CEO Walter Simmons (Demián Bichir) was scheming to harvest the power resources of Hollow Earth to power Mechagodzilla; Simmons pulls off that plan, but the result isn't what he hoped. The surge of power fries the relay (and Ren Serizawa's mind along with it) and MechaGodzilla is instead "piloted" by the remnants of Ghidorah's consciousness, which immediately kills both Walter and Ren, before going on the rampage to finish Godzilla off, once and for all.
Godzilla vs Kong is now in theaters and streaming on HBO Max.