This expansion adds, among the slew of new regular cards, two new elements to Gloom. Persistent effects are cards whose effects do not get covered up by successive cards. The guests - after whom the expansion is named - are characters that float around the board, following triggers, until they are murdered. This might mean that all those negative points you've been putting on your guest leave out the door with him suddenly, or maybe the opposite. In one game, my opponents were giving me the happiest guest imaginable... until he left the house right before I murdered him. This is my favorite Gloom expansion, as the elements it brings to the base game keep it light and entertaining, without confusing the game in mechanics. Highly recommended!