For a decade, the citizens of Phandalin have had a yearly celebration in town centered around lifting a large, enchanted ax. What can I say, other than when Phandalin was being refounded, finding anything in the ruins was cause for celebration. During the day, there is drinking, pie eating, and other small-town celebrations to commemorate the discovery of the ax and those who are strong enough to lift it.
As the sun makes it's retreat behind the trees and mountains, those of a less than righteous background head towards the direction to where the Lost Mines supposedly are said to be, and engage in a celebration of their own to test their strength in a different manner. Fists vs fists, weapon vs fist, and weapons vs weapons. The only thing banned is offensive magic, as those in The Pit do not want to attract the attention of the authorities back in Phandalin.
Price of admission is steep - you have to gain the trust of one of The Pit's members, and your safety is forfeit if you betray them. The whole region is protected from scrying, and your body will not be easily found.