The Cenobites are a twisted breed of demons originating from the works of Clive Barker, specifically The Hellbound Heart novella and the Hellraiser films and comics. They refer to themselves as explorers of the darkest regions of human experience, but more accurately they are a cult of sadomasochists who indulge in unimaginable forms of torture. They enter the mortal world in order to seek out humans of a hedonistic nature, persons who could potentially appreciate the pleasure derived from suffering. However, the Cenobites are only able to walk upon the Earth when summoned via the Lament Configuration, a peculiar puzzle box that exists on Earth for the sole purpose of being unlocked by human desire.
In the Hellraiser films, the box is normally found in the possession of a vagrant who acts as a form of herald for the Cenobites. This herald will pass on the box to those who engage in darker hedonistic practices, and when a person solves the puzzle they will summon the demons. When the Cenobites come, they subject the box-holder to the most horrific forms of torment imaginable. If they consider one worthy enough, that person is transformed into a new Cenobite. If not, they are dragged down into the Labyrinth where they are subjected to eternal "pleasure" through everlasting suffering.
The Cenobites all appear to have once been human, but their flesh is typically chalk-white and their bodies are all garbed in black leather outfits much like butchery garments. Each Cenobite is identified by their own personal disfigurements, their bodies mutilated in horrific ways, sometimes in ways that should be impossible to survive. Most of them are adorned with some manner of piercings, their flesh skewered and peeled by bizarre objects.