Giant Expeditionary Parasite.

"Urgh... And here I am, back in this place. I've got to be going crazy..." Kaizen says as he logs in and remembers that he is still inside the sea monster.

Putrid, damp air fills his lungs, bringing with it a nauseating odor. The deafening throb of the creature's heart reverberated in his ears, echoing like a macabre drum through the walls of living flesh.

"If this were an ordinary game, this should be impossible. I'm literally inside a living creature I was fighting, namely a mob..." Kaizen looks around and sees the maggots he saw last time. "And to make matters better there are other mobs in here. I have to admit that the procedurally-formed artificial intelligence the developers of this game have created is really creepy."

The repulsive maggots crawled around inside the monster, feeding on its vital fluids. The sight of those twisted and deformed bodies is a living testament to the monstrosity of this surreal environment.