Xia Mo'an, a veteran base-building and resource management enthusiast, encounters a summoning from Thaleia Ronowe, a desperate half-demon. Transported to an alien realm, he awakens trapped within an ancient cursed armor. Armed only with determination and the desolate abyss surrounding him, Xia Mo'an sets out to establish the most formidable Demon King City in the harsh Underground Demon Realm. Fortunately, he possesses the "Alien Underground Colony Construction System"—technology so advanced it rivals magic itself, where scientific principles unlock seemingly impossible possibilities. The age of Elven Lords, Dwarven Princes, and Beastkin Realms fades into history as humanity's moment arrives. The War of Four Kingdoms erupts; legendary kings clash in the Battle of Kings. Infinite worlds await exploration. Earth-Devouring Worms burrow labyrinthine passages through stone; above-ground wastelands attract adventurers seeking fortune and glory—or death. Demon lords reclaim forgotten territories. Stone Warriors march alongside Tower Mages, War Knights bolster ranks with Alchemical Cannons, and an armored phantom ruler commands them all, setting warring kingdoms ablaze. The Bloodsword Alliance stands against the Greenleaf Pact; the Iron Hall opposes the Grand Vizier's Tent. When new sovereigns challenge fallen rulers, northern winds carry echoes from Londoran's collapsed ruins, where subterranean demon worms awaken once more. Experience a ghost knight's epic saga—a tale of otherworldly reimagining, creation, conquest, and rebirth beneath the world. 【Dungeon Management + Otherworld Exploration】Inspired by Made in Abyss, Delicious in Dungeon, The Lord of the Rings, Overlord, and Dark Souls.