These are my personal ideas for my Greyhawk campaign.  Nothing in this blog or article is canon.

The Brotherhood and The Black Lilly

The Black Lilly is a large Inn located at the Southern end of the wharf in the River District, not far outside of the Cripple Gate.

The building, towers, and walls were once the barracks and headquarters of the Greyhawk city watch for soldiers and staff assigned to the River District. The location served this purpose for over a hundred years until the passage of time made the grounds increasingly expensive to maintain. Twenty years ago, the old barracks were closed, and the watch was moved to a new barracks constructed inside the city walls about two blocks East of the River Gate.

A foreign wizard eventually purchased the property, signed agreements, and greased enough palms to remodel and rebuild it into a luxurious Inn. This Baklunish warlock was an important member of a secretive organization called the Brotherhood.  

The Brotherhood is one of two large guilds of assassins within the Kingdoms of Oerth.  The other guild, being its rival, is named "The Cult of Screams Cut Short" or, more simply, "The Cult".  These two powerful guilds are opposites both in philosophy and methodology.  

The Brotherhood is a guild organized and governed by laws.  The Brotherhood can be hired to slay an enemy, but it can also be hired to protect someone, especially against attempts to poison or assassinate them.  Additionally, the Brotherhood will accept an annual payment of one thousand gold pieces to ensure they do not accept contracts to slay an individual.  Part of this fee goes to their rivals in the Cult, who also agree to refuse contracts against the person, for the most part.  Should the Cult accept such a contract against a protected person, they will notify the Brotherhood of this at least seven days in advance, allowing the Brotherhood to warn their customer and offer additional security.

If the Brotherhood is approached about a contract to slay a current client, they will refuse the contract and notify the client.  

If a third party assassinates an important client of the Brotherhood, the killer will become a target of the guild.  They will be hunted down, along with their close associates and immediate family members.

Because the Brotherhood is a guild ruled by traditions and laws, only characters of a Lawful, evil, or neutral alignment are accepted as members.

The Cult of Screams Cut Short is a religious organization. It has its own traditions and code, but these are more guidelines than strictly enforced laws. Any character of neutral or evil alignment may join the cult, provided the evil supernatural power they serve accepts them.