The Ventava Legion were a Romulan Ground Forces elite unit and considered the elite of the elite.
Comprising of only 2,000 the Legion only recruited from experienced members of the Tal Shava and Teth Koros. The admission test into the Legion is so harsh that half of the recruits will not survive. They had a reputation for their brutality when dealing with their enemies that made them infamous throughout the Alpha and Beta Quadrants. (The Dominion War Sourcebook: The Fires of Armageddon)