The Cabal was a powerful alliance of five alchemists and sorcerers in the 13 and 1400's. Eckhards is said to have betrayed and murdered almost all of them to control their secrets. The Cabal and the Lux Veritatis battled constantly, even after the disappearance of the Black Alchemist Eckhardt in 1445.
In our time Eckhardt is protected by the Cabal, who are based in Prague. They're said to be almost as dangerous as Eckhardt himself and at least as insane.
No one knows how old they really are. Bouchard claims he has seen records suggesting they were active during the Second World War, which was of course an understatement, since they go back much further than that.
The Cabal uses the Mafia front to distract attention from their real activities. But they're far more dangerous and powerful. Anyone too inquisitive about Cabal business simply disappears. They, or Eckhardt are responsible for the deaths of Werner Von Croy and Mathias Vasiley who crossed that line.
The faxes Vasiley and Von Croy sent each other were intercepted by the Cabal.
The Cabal built their stronghold in the Strahov in Prague, because they believed that the fifth Obscura Painting was hidden underneath it, in the Vault of Trophies.