The "Centipede Group", or "Centipede", is the name given to the agency behind the Centipede process. It now appears to be led by The Clairvoyant, and thus would be merely one of the many 'pseudopods' of HYDRA.
Nothing is known of this group's history or their ultimate goals. Part of their agenda seems to be in creating super-powered soldiers for their cause. Centipede shows the definitive property of the mythical Hydra, since for every 'head' cut off two more sprout in its place.
They first came to the attention of S.H.I.E.L.D. in Los Angeles, where agent Phil Coulson and his team were investigating the case of Mike Peterson, a man who had received super-powers from a Group doctor named Debbie. Debbie had administered the Centipede serum through a Centipede-styled device to Peterson and another test-subject.
When that other test subject exploded due to Centipede's use of the unstable Extremis process, Peterson saved Debbie from the destruction of the lab. Rather than thank him, Debbie told him to disappear rather than compromise the secrecy of the project.
When Peterson seemed also on the verge of destabilizing, Debbie dispatched an assassin to ensure his silence. The assassin was stopped by S.H.I.E.L.D. agent Melinda May and Peterson taken off the grid by S.H.I.E.L.D., who managed to stabilize the Extremis reaction. 
Chan was brought to a nearby lab where Debbie managed to harvest the fire-resistant platelets in Chan's blood. The platelets allowed the Extremis element of the Centipede process to be stabilized without the explosive after-effects. Having gotten what they needed from him, Debbie ordered Chan be drained, killing him.
But before that could happen, Chan was released by a S.H.I.E.L.D. extraction team led by Phil Coulson and agent Kwan Chen. Unfortunately, Chan (Now going by the name "Scorch"), was tired of S.H.I.E.L.D.'s interference in his life, and killed Kwan. Chan then confronted Debbie and Raina. Raina abandoned Debbie, leaving her to be incinerated by Chan. Raina escaped, but the lab was destroyed when Chan detonated from an Extremis over-dose.
Before the destruction of the lab, S.H.I.E.L.D. consultant Skye managed to extract a few files from the building's mainframe, hopefully enough to give S.H.I.E.L.D some new leads on their activities.
Raina was last seen at a penal facility at an unknown location speaking to a prisoner named Po. Raina informed Po that "Stage One" of project had been completed, and that they were moving into "Stage Two". She also passed along the request of the Group's unknown leaders that Po contact a mysterious individual known as "The Clairvoyant" for any insights he might have as to "Stage Three". At this juncture, The Clairvoyant apparently lost faith in Po, since soon afterwards, during a telephone conversation with Raina present, the group leader electrocuted, or killed in some similar manner, Po. 
Known Subjects Edit
- Agents of S.H.I.E.L.D.