Black Chamber
From the Metal Gear Wiki
Black Chamber was a Special Forces group founded after the Outer Heaven Crisis to act as a sort of "shadow FOXHOUND." After Solid Snake's sucess with Operation Intrude N313, FOXHOUND became to well known to the general populace and was therefore under closer surveillance by rival intelligence bodies. Black Chamber was founded to perform operations that FOXHOUND would perform normally, but they weren't under surveillance like FOXHOUND was at the time.
Two years before the Galuade Incident Black Chamber was ordered to retrieve a U.S Built Metal Gear, which had been seized by South American terrorists at the time. Black Chamber succeded in destroying this Metal Gear, but the U.S government feared that Metal Gear's construction and Black Chamber's existence would be revealed to the public, so the unit was attacked by FOXHOUND (under Colonel Campbell's command, though he was told they were terrorists) shortly after their return home.
Only five members survived that attack, but they escaped, vowing revenge against Solid Snake, Colonel Campbell and "Anonymous," the man who had ordered their termination. They became mercenaries until they later resurfaced as terrorists during Project: Babel during which the remaining five members were killed.
