Vir Cotto arrived on Babylon 5 in 2258. He was the joke of his family and only became Ambassador Londo Mollari's assistant because no-one else wanted the job - Mollari too was nothing but a joke and the station was concidered too dangerous a place because of the fate of its four predecessors. Vir's family saw the job as a perfect opportunity get rid of him, but Londo wasn't too thrilled to have the young and clumsy Centauri as his assistant either. Still, as time went by the two became good friends - so good, in fact, that when Londo acquired more power and the court decided that he needed a better assistant than Vir, the Ambassador overrode the decision and allowed Vir to stay.

Vir had been suspicious of Mr. Morden from day one and had often warned Londo of his associations with this shadowy man. When Londo too began to see the error in his close relations to the Shadows, he decided to send Vir away to ensure the safety of the naiive attache he had become very fond of. In 2260, with the help of Delenn, he then arraged Vir the post of Centauri Ambassador on Minbar. Vir had always felt sorry for the Narn and immediately took advantage of his new position to help them in their plight under the Centauri rule. He himself had no means to help the them, but he used his connections to create an imaginary Centauri official named 'Abrahamo Lincolni who he then used to have over 2000 Narns transferred from the Narn Homeworld to various workcamps near Centauri Prime. Once the Narn arrived on the camps, they were declared dead and then smuggled to neutral planets. Unfortunately Commander Ivanova and Captain Sheridan, unaware of Vir's true intentions, brought his underground Narn railroad to Londo's knowledge who then immediately had Vir removed of his position.

Vir's pro-Narn attitudes ruined not only his diplomatic career on Minbar, but also his arranged marriage with a woman named Lyndisty. She was the daughter of a Centauri official who had been responsible of "culling the herds" on the Narn Homeworld and thus her opinions on the intelligence and worth of Narns differed greatly from Vir's. Still, the final reason for why they were never even married was that after Vir lost his job at the embassy, he was no longer important enough for Lyndisty to marry.

Despite Vir's misuse of authority, he and Londo restored their friendship by early 2261 when Londo turned to Vir for help in the assasination of Emperor Cartagia. When the hour came to actually kill the Emperor, Londo failed and Vir was forced to inject the Emperor with a deadly poison.

Vir had often acted as Londo's replacement as the Centauri Ambassador and when Mollari finally became the Emperor in 2262, one of his first actions was to appoint Vir as the official Ambassador. His reason for this was not only that he trusted Vir more than any other Centauri, but also that he now knew about the Drakh forces on Centauri Prime and wanted to protect Vir, to keep him as far away from the homeworld as he could. Still, not even Babylon 5 was safe place for Vir. Some of Londo's political adversaries sent Lady Mariel, the Emperor's ex-wife, to Babylon 5 with to seduce Vir in order to gain information from him. For a while Vir was ecstatic that a woman like Mariel was interested him, but the truth soon hit him. By now Vir was already involved with a group of techno-mages plotting against the Drakh and with their help he found out about Mariel's true intentions and took revenge - Galen cast a spell on Mariel making her really fall in love with Vir.

With the help of the techno-mages, Londo's wife Timov, and Mariel, Vir began to slowly understand what was really going on on Centauri Prime - that the Drakh were in control. He went undeground and formed a resistance movement called "Legions of Fire" to fight the Drakh. He didn't want the Interstellar Alliance to get involved - he had already once saved Sheridan's life unbeknownst to the President - and kept his work secret sabotaging the Drakh warmachines and slowing their preparations down without actually revealing himself.

All hell broke lose in 2278 when the Drakh kidnapped Sheridan and Delenn's son David. Vir was forced to act openly, but fortunately he had prepared for this. With one swift precise hit his forces brought down the Drakh, though not without casualties - the Drakh had planted fusion bombs around the palace and managed to detonate one of them before their defeat. Sheridan, Delenn, and their son were freed as was Centauri Prime. Unfortunately Londo and G'kar were killed in Londo's last desperate attempt to escape his keeper.

In 2260 Londo had sought advise from Emperor Turhan's prophetic widow, Lady Morella. In addition to telling Londo's future Morella had revealed a part of Vir's future as well - namely that he would become the Emperor after Londo's death. In 2278, when almost twenty years had passed, the prophesy came true.