Subterranean People

These beings keep a loosely human silhouette, though the details set them apart: two toes on each foot and three fingers on each hand. They deck themselves in golden or metallic trinkets, wristbands, necklaces strung with round beads, and plating over the right shoulder. Each one hides its face inside a distinct helmet patterned after Jomon pottery, leaving only a pair of round eyes visible. Their bodies vary wildly in scale, from squat, rounded little figures to hulking muscular giants.

Brimming with ambition, the race set out to take the Earth for itself, only for that swagger to crumble once their king was defeated, exposing a deep vein of cowardice as they fled. Ironically, they were gifted builders, having carved out the very stronghold the Monster Association would later occupy. In Saitama's dream they loom far larger and deadlier than reality, ranging from twice a person's height to skyscraper proportions, an exaggeration of his imagination, though genuinely enormous variants did exist, later seen when Phoenix Man reanimated their colossal corpses.

When a hand bursts through Saitama's apartment wall and flings him into the street, he meets the Subterranean People, who savage him, boast of the humans they have slain, and stake their claim to the world. A massive brawl follows before he emerges the victor, and just as the king steps up, Saitama wakes to find it was only a dream. The real invaders then arrive, but their king drops after one kick and the rest prove far smaller and weaker than the nightmare version, quickly retreating below. Their end comes later: their unity fractured into civil war, and Child Emperor and Phoenix Man eventually stumble into a pit heaped with their dead. Do-S is said to have brainwashed the last survivors into slaughtering one another, and the reanimated corpses Phoenix Man raises are finally put down by Child Emperor and Saitama.

Within Saitama's dream the Subterranean People delivered the hardest fight of his life, packing the strength, toughness, and sheer numbers to match his power, strong enough to make him bleed with one punch and durable enough to shrug off serious blows. Reality is far less impressive: most are small and timid, surrendering rather than fighting, yet even so a swarm of them managed to restrain Brave Giant, and their disaster ratings still span Tiger to Demon. They outmuscle regular humans, and their feet are their most dangerous weapons, hardened by a lifetime of pushing through the harsh underground. Their combat leans on coordinated hand-to-hand striking, including a forceful Subterranean Kick that several of them may combine into one blow and a Cooperative Attack in which a group surrounds a target to hit it all at once. Some also carried swords, blades that could be seen scattered among the corpses in their burial pit.