The name of the society changes with the current lingua franca among mortals. For much of the early and late modern era, they were known as Les Amis Noirs. In the Dark Ages, this shadow council was known as the Amici Noctis. Before the rise of Rome, they were called Brether Nokw and during the reign of the Ashirra, the Friends of the Night were known as the Asdiqa al-Lail.
The Friends are an initiatory society: members are invited at the behest of existing members, and candidates are tested both formally and informally before being invited. A vampire is considered for membership only once, and any candidate who is rejected will never join the society. Every Lasombra except the most dullard amongst the clan knows that the society exists, but the only ones who know significant information about the society are members.
The Friends of the Night ensure that the clan runs smoothly, essentially preserving the internal status quo while slowly advancing it to closer fit their vision. In accordance with the Lasombra predilection for power from the shadows, the Friends of the Night generally ensure this smooth operation through ruthless behind the scenes manipulation, well placed words in well placed ears and the occasional discreet assassination. The most infamous practice of the Friends is its role in managing diablerie within the clan, usually through Courts of Blood. The Lasombra believe that if diablerie exists, somebody is going to do it, and they would rather that it be applied productively. After all, proximity to Caine is an investment, and that investment can be spent wisely, or transferred to a more responsible keeper.