Auctions are lots of treasure that characters can create and bid on. To start an auction, go to your character sheet's treasure page, click the item you want to auction, and then click the Auction button.
Dusk Fern Powder
Quality 3 Dust
Rune of Indefensible Slaughter
Melee "Pierce 2 Crit" on Melee Weapon or Wraps
Quality 2 Poison