He was a supporter of Romana II during her civil war with Pandora; she regarded him as her figurehead within the walls of the city while she was in hiding in the Outlands. At first he appeared to be strong ally of Romana's, but he soon showed an independent streak and his own agenda. After Romana's return to the city, Matthias held secret meetings with Darkel, the chief strategist of Pandora's forces, unbeknownst to Romana. Matthias gave a disc to Commander Hallan, aware that it might be infected with the Dogma Virus. Hallan was forced to enter stasis to await a cure. Romana and her supporters were deeply suspicious of Matthias' motives thereafter. When Romana and K9 entered The Matrix to imprison Pandora again, Matthias lured Darkel, with the prospect of further secret negotiations, to the Time Lord Academy, where she was taken prisoner by Coordinator Narvin. This led to the victory of Romana's side, but she was greatly weakened by the experience.
During Romana's recovery, Narvin suggested that Matthias should be acting President, but Matthias pointed out that Valyes remained Chancellor (though appointed by Pandora), and was therefore acting President. In the immediate aftermath of the war, an alien invasion threatened to devastate Gallifrey, and Matthias undertook negotiations with the invaders. As the invasion escalated, Valyes appointed Matthias as Lord Cardinal with the powers of a Chancellor. Valyes pardoned Darkel, resigned as acting President, and appointed her as his successor. Romana disputed the legality of his actions, as she was still technically President. Matthias counter-claimed that as acting Chancellor he, rather than Darkel, was Valyes' rightful successor.
In the elections to decide the matter, Darkel and Matthias agreed to the arrest of Romana for high treason, barring her from running. Matthias reminded Leela of Braxiatel. This was astute as he had been working with the former Chancellor to be made President. Before the election results were announced, Braxiatel turned up, having conspired with Matthias and Narvin. He claimed the Presidency for himself. As Romana's edicts had been revoked, he was still Lord Chancellor and therefore acting President. After freeing Romana and allowing the Pandora creature to consume Darkel, Braxiatel resigned and, to everyone's surprise, named Matthias his successor as Lord President, before returning to his exile.
Matthias' presidency was over a world that was decimated and ravaged by economic ruin and disease. The Free Time virus was still active, and regenerating Time Lords were 'zombified' in their thousands. Matthias nominated Romana to undertake a mission to locate the cure, following which she would have to go into exile. Romana's K9 opted to remain on Gallifrey in the employ of Matthias, helping combat the virus. Leela also chose to stay and live the rest of her life on Gallifrey, near her husband's grave. Romana followed the coordinates given to her, only to find Braxiatel. Braxiatel had manoeuvred Matthias into the position of President in order to save Romana from having to "go down with the sinking ship" as Gallifrey plunged into chaos. (AUDIO: Fractures, Warfare, Appropriation, Mindbomb, Panacea)
Matthias quarantined those infected with the Dogma virus, and waited for the problem to solve itself. Once his orders had been carried out, Matthias exiled himself to the wastelands of Gallifrey. (AUDIO: Ascension)
Alternative Gallifrey Edit
In an alternative timeline in which Rassilon failed to finish the Eye of Harmony before his death, Matthias was a commentator on the Gallifreyan vidcasts, often presenting the leading stories. (AUDIO: Emancipation, Evolution, Arbitration)