The 10 Dons (
The 10 Dons would gather once a year at the start of September for the Underground Auction. During that time, they would discuss their plans and issue orders, which would then executed by their special bodyguards, the Shadow Beasts, each of whom was the most powerful Nen user in the service of one of the Dons. They were known to hold Neon Nostrade's fortunetelling abilities in high regard. It would also seem they held an immense amount of combined wealth, which was enough to allow hiring a team of 9 Nen-capable freelance assassins, where two of which were the Zoldycks, all at once. They also knew about the existence of Nen.
Yorknew City arcEdit
Through Neon's predictions, the Dons begin to suspect there might be problems with the Underground Auction, so they send Owl to relocate all the loot. After a large number of Mafia members and auction clients in Yorknew City are massacred by the Phantom Troupe, the Ten Dons send the Shadow Beasts to deal with them. The Shadow Beasts are killed in the ensuing fight, prompting the Dons to put a bounty on the Spiders' heads and hire a team of assassins, including Kurapika, Zeno and Silva Zoldyck. The leader of the Troupe, Chrollo Lucilfer, kills all but the latter three. Before the two Zoldycks can take him out, the 10 Dons are assassinated by Illumi, invalidating their contract. Illumi then controls their corpses to start the Underground Auction and cancel the bounty on the Phantom Troupe.