The evidence includes three new Achievements that has the player discovering "all named locations in Oasis and the surrounding Pirate's Booty areas." The other Achievements include Treasure Hunter and Completionist.
On the Gearbox forums, some gamers have found new sound files for the unannounced DLC which announces, "Legends speak of Captain Blade's Lost Treasure of the Sands. Of a prize so great, that men would turn the sands red in pursuit of it. Of a pirate queen, courageous and deadly, who would stop at nothing to find it. Of a monstrous Leviathan. Of the Vault Hunters who journeyed to the desert town of Oasis, not knowing the horrors that would befall them."
More leaks about the DLC claim it'll also introduce a new head for each class, a new rarity level, and new items, weapons, and bosses.