The Mafia's underground auction is an annual event held at the beginning of September in the Cemetery Building in Yorknew City. Usually, all the Mafia clans send their high-ranking representatives to attend the auction, and some Mafia bosses even go to the auction themselves, because it is the place where they can show off their wealth to the Mafia Community and make a name for themselves. There have been cases of Mafia clans going bankrupt due to bidding too high at the auction.
The underground auction that takes place in September 2000 is notable for being involved in a series of violent incidents:
On the night of September 1st, the Phantom Troupe attack the Cemetery Building to steal all the auction items, killing all the Mafiosi and clients there. Not knowing that the Owl of the Ten Shadow Beasts has already moved the items to a safe place, the Mafia Community mobilizes a large number of members, including Kurapika and some bodyguards of the Nostrade family, to chase after the Troupe to the Gordeau Desert.
Their superior number and conventional weapons however are no match for Uvogin of the Troupe and another massacre takes place. Four of the Shadow Beasts then arrive at the battlefield and attack Uvogin together. They manage to injure him but eventually are all killed by him. Kurapika then takes the opportunity to capture Uvogin off-guard using the Chain Jail. The Phantom Troupe immediately go after Kurapika and his colleagues but their car is stopped on the way by the arrival of the remaining Shadow Beasts. The Troupe capture Owl and kill the rest with ease.
They quickly find out where Uvogin is held captive and free him after killing Dalzollene, head bodyguard of the Nostrade family. On the night of Septerber 2nd, Uvogin is killed in a duel with Kurapika in the Gordeau Desert. To avenge him, the Phantom Troupe attack the Cemetery Building again on the night of September 3rd, killing approximately 2,000 Mafiosi and some professional assassins hired by the Ten Dons. After the Ten Dons are killed by Illumi Zoldyck, the Phantom Troupe create fake corpses of themselves, disguise as Mafia members, steal all the items and continue the rescheduled auction using the copies that will disappear in 24 hours.