Morlocks are subterranean creatures evolved from humans in the far future. More famously depicted as sloth like in the 1960 George Pal film version of The Time Machine, H. G. Wells described them in the 1895 novel as more apelike, living a troglodyte existence in which they maintain ancient equipment they have lost the ability to use properly.
In the novel, Morlocks have a sinister symbiotic relationship with the Eloi, a childlike race who live a banal life of ease on the surface world. The Morlocks feed, clothe, and provide infrastructure for the Eloi. In exchange, the Morlocks eat the Eloi. The Time Traveler surmises the relationship between the Morlocks and the Eloi originated as a rigid class structure in which the Eloi were the wealthy leisure class who enjoyed the benefits of the working class Morlocks’ labor. At one point in time, the Morlocks ran out of food, presumably because of disinterest in their plight from the upper class eloi, and decided to use them for food. Eat the rich, as it no?
The social commentary loses something in the pal film. The Eloi are depicted as small, blonde haired, blue eyed “human vegetables,” as the Time Traveler describes them. They are good looking, but docile and devoid of any real emotion. They have let their historical records turn to dust, so they have no interest in who they are or from what they came. The division between the eloi and the Morlocks was caused by a nuclear war. The Morlocks ran underground to save themselves from the decades-long bombardment and remained underground. The Morlocks use old air raid sirens to lure the eloi into caves so they can eat them. The clas struggle element is completely gone. Indeed, the time traveler convinces the weak Rloi to fight the Morlock monsters and they quickly defeat them because the morlocks have never before faced opposition.
Try not to dwell too much on the implications of a blonde haired, blue eyed Aryan leisure class getting off their duffs to eliminate the only group of people who know how to maintain the society in which they live. One can only assume class warrior the Time Traveler the ensuing starvation/genocide is a small price to pay for progressive social justice.
Political and social issues aside, Morlocks have become a staple of science fiction novels, comic books, films, and television episodes. Authors as diverse as J. R. R. Tolkien and Larry Niven have used variations on the concept. A group odf mutants living under New York City in the X-Men are referred to as Morlocks. I am skipping talking about the 2002 filmed remake of The Time Machine since everyone else did as well, but the camp classic horror film CHUD has Morlock elements in its antagonists. Even the Sixth doctor faced a race of underground reptiles named Morlocks when he traveled to te far future with H. G. Wells. The critters have definitely reached icon status. They have even gone after Sheldon Cooper as of late.