We do only what we're meant to do.”
― The Keymaker[src]
The Keymaker (sometimes spelled Key Maker) was a program created to open up the door to the Source for The One. In the Sixth Matrix he was kept prisoner in the Chateau of the Merovingian, during which time he saved Niobe and Ghost from an Agent. Morpheus, Neo and Trinity, with the help of Persephone, manage to free the Keymaker.
While he was imprisoned, Abel and Cain let him escape, allowing him to save Niobe and Ghost from an Agent. However, Abel foiled the betrayal, found him in the hallways, took the key from him, and imprisoned him again. The Merovingian destroyed the key, but Niobe and Ghost still escaped, with the Keymaker apologizing to them for his decision to meet them ahead of schedule.
Morpheus, Neo and Trinity were later led to the Chateau by Persephone, where they freed the Keymaker. During their escape, the Keymaker provides Trinity with a key to start a motorcycle. Agent Johnson attempted to kill him, but was stopped by Morpheus. Neo eventually arrives to rescue him and Morpheus, narrowly avoiding an explosive collision between two trucks on the freeway.
The Keymaker explained how the resistance could access the door to the Source, both in terms of how they could find the door and the precautions that had to be taken to allow them to open the door without triggering the security systems.
Just outside the door to the source, The Keymaker is shot by the Smiths. His last words were to assure Neo that he was at peace with his death and to direct Neo and Morpheus to the doors that would take them to their next destinations.
The New Matrix
After his death, his chain of keys were in the possession of the exile known as the Landlord. His brother, the Boxmaker, blaming the Merovingian for his death, got revenge by creating box-like portals to the Merovingian's prison constructs in the form of heavy and small boxes called Pandora's Box, unleashing powerful exiles onto the Matrix world, causing havoc.