The Hydra Hero: Ghidorah

Those who read the novelization of or saw the movie "Godzilla: King of the Monsters" probably know about The ORCA and Alan Jonah. The ORCA was a device created by Monarch that is used to replicate the bioacoustics used by Titans, effectively communicating with them as well as controlling them to some extent by replicating the commands of Alphas. Alan Jonah is a cold-hearted ecoterrorist who purchased the Ghidorah's left head after it was decapitated by Godzilla off the coast of Isla De Mara. Those who read the novelization of "Godzilla vs. Kong" probably know that Alan not only found another of Ghidorah's heads, but then sold both heads, now skulls, to Walter Simmons. He is the CEO of APEX Cybernetics and managed to use his resources as well as the skulls to build a weapon that could take Earth back from the Titans and have mankind remain the Alpha species of the planet. This weapon was named Mechagodzilla, but it needed a unique energy source to allow it to fight at max capacity. After being charged up by the Hollow Earth element, the restless spirit of the Ghidorah skulls possessed the Mech, and it nearly managed to kill Godzilla. However, Kong managed to intervene, resulting in the Mech's defeat. Most thought that this was it for Ghidorah, but they couldn't be more wrong.

Because...

Ghidorah is not a physical kaiju, made of flesh and bone.

Ghidorah is a conscience.

A menace forever haunting Godzilla.