Liar's Night was a holiday celebrated in Waterdeep on the 30th day of Marpenoth, paying tribute to the deities Leira and Mask. It was celebrated to appease the gods and guard against their unwanted attention. It was held in Waterdeep in the late 15th century DR.
Liar's Night was celebrated by donning costumes or glamers to disguise one's self and pretend to be that which they were not. Common masks included the symbol of Mask himself and the mirror masks of the priests of Leira. Though there was no limit on the disguise someone could wear, the more elaborate the costume, the more celebrated the wearer.
The celebrations began in the evening when people placed candles into gutted pumpkins or gourds that had faces carved into them. Each pumpkin represented a person who had donned a mask, while the candle light represented who they truly were. For as long as the candle was lit, lies told and embarrassing acts wouldn't harm a person's reputation. As such, celebrations often devolved into chaotic anarchy. Bad luck came to those who returned after celebrating to find their pumpkin's candle had gone out. Intentionally blowing out someone else's candle or smashing their pumpkin risked drawing the ire of both Mask and Leira.
Tricks, pranks, and even pickpocketing were common on this night; thus tradition had people filling their pockets with candy in lieu of money. Pickpockets took the candy and replaced it with a small token such as a folded scrap of paper, or a trinket. More commonly, people just traded candy at face value, and readily handed it out to children who asked. Illusionists and stage magicians were often hired to perform or wandered the streets in hopes of garnering clients.
It was known that no deals were to be made, nor contracts signed on Liar's Night, as nobody trusted that the other parties would honor their commitments.