Following the death of Emperor Turhan and the murder of Prime Minister Malachi, Lord Refa and Londo Mollari placed young Cartagia on the throne. Refa encouraged him to make war on all around their borders before his death.
Cartagia later decided to make Londo Mollari Minister of Security, after a request from Mr. Morden. Londo returned to Centauri Prime to discover that Cartagia was insane. Those who spoke ill of him disappeared and had their heads placed upon a table, which he dubbed his Shadow Cabinet. He would speak to the heads late at night. Cartagia later made a deal to allow the Shadows to use the island of Selene as a base on their world.
Cartagia later confined in Londo that he wanted to be a god, to be worshiped, and Londo decided that he must kill him. Along with Vir Cotto, Londo conspired to assassinate the mad emperor. Cartagia had G'Kar captured, and tortured him for a very long time, but grew angry when G'Kar wouldn't scream. Cartagia said that if G'Kar didn't scream, he would be killed. Londo brought G'Kar into his plan, and agreed to free Narn if G'Kar helped him remove Cartagia from the throne.
When it was discovered the Vorlons were destroying all the worlds where the Shadows had influence, Londo tried to persuade Cartagia to order the Shadows to leave, but Cartagia refused, saying he wanted to turn Centauri Prime into a pyre to light his way to godhood. Londo later persuaded Cartagia to have G'Kar tried on Narn to make an example of him, to which Cartagia agreed. Before leaving, Cartagia was offended by the way G'Kar looked at him and ordered his eye to be plucked out. Upon arriving on Narn, Cartagia held the trial, but G'Kar managed to escape, and the other Narn began to riot. Londo pulled Cartagia aside and tried to stab him between the hearts with a poison-tipped needle, but failed. Cartagia was killed when Vir picked up the needle and stabbed him in the chest.
- One of the Babylon 5 novels identify Cartagia as Narleth Jarn.
- Babylon 5: