Carmen Santacosta was an Adjudicator.
Aware of subspace experiments on Mars but Unable to generate a stunnel to get there, they arranged for a shuttle to crash near Antony McGuire's expedition. Santacosta, an Oberon Special Operative claiming to be a lounge singer who survived the crash, joined the group. The Adjudicators expected the expedition would be able to find out what was really happening at the Martian North Pole. She killed Vince Esteban since he was a suspected Martian Axis and might interfere with her mission.
She brought along a Transit-web which acted as a portable stunnel terminus, so she could bring more Adjudicators when she reached her destination. Santacosta reluctantly allowed the Seventh Doctor to use it to destroy the GodEngine. (PROSE: GodEngine)