Disciple of the Three Kings

Chaos descended upon the world as portals to other dimensions erupted, unleashing monstrous hordes. With humanity teetering on the edge of annihilation, the martial arts realm of Eun, the magical kingdom of Ainhalt, and the mechanized realm of Gehenna converged, their superpowered inhabitants rising to confront the monstrous threat. Yet, these heroes were far from benevolent. They subjugated Earth's newly empowered "players" under a brutal law of the jungle. Lee Ro-Woon, a beacon of hope, sought to unite the players and the interdimensional invaders for a peaceful coexistence. Betrayed by his allies and ostracized by the otherworldly powers, Lee Ro-Woon was cast into the abyss, his spirit broken and his dreams shattered. On the brink of despair, he contemplated giving up on everything, when he became the vessel of chaos and was transported to a sealed world. There, he encountered three supreme beings. Lee Ro-Woon becomes the disciple of the Three Kings and rises to rule over everything!

(Source: Kakao Entertainment Corp., translated)