Longest night (Dark Moons 33) is, as you can guess, the longest night of the year. Traditional celebration of Longest Night involves family gathering around the primary hearth or fireplace in the home and keeping a fire burning all night. They tell stories of the ancestors or the heroes of the area. Some areas have evolved this into an entire village or town gathering around a central bonfire and telling the history of the area, especially stories of heroes from that village/town.
In certain parts of Shaintar, most pointedly the Kal-A-Nar Empire, Longest Night has become something else entirely. Larger towns and cities in the Empire have turned this holiday into a night of drunken decadence, depravity, and lawlessness; a true bacchanalia.