The Clockwork are a group of autonomous robots that operate in the City of Heroes MMO.
For the Clockwork of the Praetorian Universe, check out Praetorian Clockwork.
For Psychic Clockwork of Universe Epsilon Tau 27-2, check out Psychic Clockwork.
Nobody really knows how the Clockwork got started. According to Blue Steel, the first instances of the Clockwork were the appearance of small robots that were dubbed "Sprockets". These "Sprockets" were stealing metal and wires, and were seen more an nuisances than a real threat. Still, when they began stealing larger parts, that got the attention of Paragon's first superhero policeman.
Blue Steel's investigation led to an abandoned warehouse, where the Sprockets were giving the material to an unidentified man. Blue Steel gave chase, but the man eventually died. It was not known if the man's death was caused by injuries during the confrontation or because of Blue Steel's uncharacteristic brutality. Either way, the man's body could not be retrieved, and the matter was considered closed.
After the First Rikti Invasion, the Sprockets returned, but this time were welcomed by the city because they appeared to be cleaning up the damage and debris. In truth, however, the little robots were once again collecting metal and wires for their main purpose of creating still more robots. This time, though, they were creating larger and larger units.
Then came the news that the Clockwork had a leader... a "Clockwork King" that had a very human brain inside. Was this the man that Blue Steel chased before? Nobody knows.
(For more information about the Clockwork, check out their entry on the Paragon Wiki.)