Rex is a LitRPG player who gets transported into a fantasy game world during a major battle between a massive human infantry and hordes of monstrous beasts. Appearing in the thick of the chaos, Rex is immediately attacked by human soldiers who assume he is a hostile monster. While fending off the attackers, Rex accidentally dispatches a soldier using his enhanced strength and combat abilities from the game.
Rex flees the battle but is hunted down by a group of elite soldier trackers. Badly wounded, he is cornered in an isolated mountain cave and falls into a deep crevasse. When he awakens, Rex finds himself amongst the monsters in an underground lair. Though initially suspicious, Rex uses his knowledge of the LitRPG lore to convince the beast tribe leader he was outcast as a freak from birth.
Rex proves his usefulness, battling apelike minotaur warriors who challenge the tribe leader for power. As Rex gains the beasts' trust, odd behavior points to the monsters being manipulated by a sinister mind control. Rex speculates a nefarious third party is orchestrating the conflict from the shadows.
Rex gains access to the monsters' main headquarters where a glowing orb radiates ominous waves of energy. Rex sneaks past the guards and incapacitates the orb's magic, freeing the monsters from its mental grip. Rex escapes the lair amidst violent shaking and collapses, realizing the "orb" was actually an egg - and he just unleashed its terrifying hatchling.
Rex leverages his hero status with the newly sane monsters and human combat engineers to construct battle mechs to confront the giant winged beast now seeking mayhem in the city. After fierce urban combat, Rex manages to draw the monster back to its nesting ground inside the mountain.
In an epic final showdown, Rex lures the beast into sealing the mountain cavern entrance on itself, trapping it inside. Rex rejoins society as savior and mediator between men and monsters forging a lasting peace. But dark rumblings foreshadow a new threat incubating deep within the sealed chamber...
