Irving Marion Lambert was born in 1961 in Batcave, North Carolina. He is a high ranking officer in the National Security Agency, where he holds the rank of Director of Operations for Third Echelon.
Colonel Lambert is the director in charge of all Third Echelon field operations and he answers to the Director. He became involved in intelligence as a young man and rose quickly in rank and responsibility. He was in the Persian Gulf for months leading up to Operation Desert Storm, coordinating SIGINT and running double agents. Once the war began, he was aiming lasers and arranging for television coverage of the good parts. He is a popular and well-connected man in Washington, D.C., although minimally trusted and never publicly acknowledged.
In the Splinter Cell series, Lambert is the leader of the Third Echelon team, and thus Sam Fisher's "handler". His role is to guide Fisher through each mission over the cochlear implant radio, providing information such as critical updates, objective changes, and enemy status. After many missions Lambert becomes one of Sam's closest and most trusted friends.
Many of his duties involve conveying intelligence to Sam and other Splinter Cells while they are 'on the job'. He also handles the bureaucratic and political aspects of espionage. Lambert has a much more no-nonsense approach to missions, in contrast to Fisher's aura of dark humor.
In 2008, Irving is kidnapped by John Brown's Army, and his possible death is determined by Sam. Sam can decide to shoot Lambert or Jamie Washington in the Current-Gen version of "Double Agent" (though even if Lambert is shot he still survives in the immediate aftermath as Fisher tells him to "hang in there"). In the Last-Gen version, Sam can decide to either upload information that either blows Lambert's cover or enhances it, increasing Lambert's chances of survival. If the player increases Lambert's cover, it is revealed at the end of the mission that Dufraisne "roughed him up pretty badly" but does not kill him. If the player blows Lambert's cover, Lambert is shot and killed at the end of the mission. In Splinter Cell: Essentials, Sam is only given one option, to shoot Lambert to keep his cover, an act that leads to Williams trying to frame Sam for murder of Lambert in cold blood.