Big Sal is Nero's right hand man and is involved with a variety of sneaky operations with Nero, Clanden and Troike. He can be found at the Gomorrah casino on The Strip. Most of the time he hangs around in the hallway near the Zoara Club, upstairs from the Brimstone main hall. At night he can be found in his room in the southwest corner of the suites level.
Big Sal will disappear from his office and the casino following a pro-Nero/Legion completion of How Little We Know. The same will happen if you fail the quest by killing Clanden or otherwise causing the Omertas to become hostile to you.
When he is killed a message pops up to tell you that he has died, much like a companion in Hardcore mode.
Big Sal is voiced by Alex Rocco. Big Sal may be a nod to his most famous role as Vegas Mob boss Moe Greene in 1972's The Godfather.