Senator Vreenak was a key member of the Romulan Senate from 2360 to 2374. He was also the vice-chairman of the Tal Shiar, secretary of the War Plans Council, and one of Proconsul Neral's most trusted advisers. Vreenak is perhaps most well-known for negotiating the non-aggression pact between the Romulan Star Empire and the Dominion in late 2373. One of the most ardently pro-Dominion senators, Vreenak had very little faith in the Federation-Klingon alliance's chances against the Dominion.
In 2374, Vreenak attended a high-level diplomatic meeting with Weyoun on Soukara. Captain Benjamin Sisko convinced him to make a secret detour to Deep Space 9, to view supposed evidence of a planned Dominion invasion of Romulan space. However, Vreenak discovered that the evidence had been forged, and headed back to Romulus threatening to expose the plot for all to see. En route, his shuttle exploded, a result of sabotage by Elim Garak that was intended to both eliminate the Senator as an adversary and provide a plausible explanation for any flaws in the forgery.
A subsequent investigation by the Tal Shiar uncovered the fabricated evidence, but its defects seemed to be a result of the explosion. The Romulans logically concluded that the Dominion had assassinated Vreenak to prevent him from returning to Romulus with the evidence, and joined the Dominion War on the side of the Federation and the Klingons. (DS9: "In the Pale Moonlight")
"It's a faaaaake!"
- - Vreenak
"So you're the commander of Deep Space Nine. And the Emissary of the Prophets. Decorated combat officer, widower, father, mentor, and... oh, yes, the man who started the war with the Dominion. Somehow I thought you'd be taller..."
"Sorry to disappoint you."
"To be honest, my opinion of Starfleet officers is so low that you'd have to work very hard indeed to disappoint me."
- - Vreenak and Benjamin Sisko
"You are persistent, captain, I'll grant you that. But dogged determination isn't enough to change the reality of your situation. Time is definitely not on your side. The Dominion shipyards are working at one hundred percent capacity, yours are still being rebuilt. The Dominion is breeding legions of Jem'Hadar soldiers every day – you're experiencing a manpower shortage. But most important, the Dominion is resolved to win the war, at any cost."
- - Vreenak
The Lost Era novel Serpents Among the Ruins gives his first name as Merken, and indicate he was in public service around 2311, the year of the Tomed Incident. He is shown as one of the senior aides to the Romulan ambassador during negotiations leading to the Treaty of Algeron, and is a staunch Romulan nationalist and supporter of the novel's antagonist, Admiral Vokar.