Omertas

The  is a faction that controls a section of New Vegas.

Background
The Omertas are a somewhat shadowy faction who control the Gomorrah casino. They're based on the Mafia.

Interactions with the player character
The way to come across the Omertas is through the main storyline. For various organizations you are asked to get in contact with the Omertas at some point. You start out a quest with them when you're asking around to know what the family has been up to. A member of the family comes up and asks why you've been asking questions about them. To get info out of him you must enter his room and steal his diary from his desk. At this point there are many ways to go about this so no need to explain in great detail. After you finish the quest the Omertas should Idolize you in the General section on your Pip-boy.

Appearances
The appear in Fallout: New Vegas.

Behind the Scenes
Omerta is the code of silence in Sicillian/Italian organized crime organizations.