The expansion adds one player and 55 cards to the game. Here is a description of the expansion from the publisher:
In the Gloom card game, you make your eccentric family of misfits suffer the greatest tragedies possible before helping them pass on to the well-deserved respite of death. Just mix the 55 transparent cards included in this set together with your copy of Gloom to add morbid new Modifiers, Events, and Untimely Deaths, and a new family -- the artistes of Le Canard Noir, whose creative endeavors always end in disaster.
When art lets you down, the Black Duck is there for you. This dingy cafe is home to a motley assortment of washed-up bohemians. Here the tormented painter Rosseau buys drinks for neurotic models and destitute poets, while a troubled actress and sickly courtesan compare notes across the way.
Also included are five Residences with a light blue background behind their central illustration. These are each placed next to their related family at the start of the game. New cards called Mysteries, which have a dark blue effects bar at the bottom, are also shuffled into the deck before play. A Mystery is the only card that can be placed on a Residence (and only a Residence), and can be placed on any Residence as either of your two plays. It gives that Residence's player a special effect and Pathos points that count toward his final Family Value. A Mystery remains even if the requirements for playing it are lost. You may discard a Mystery from your hand as a free play.