If multiple players have Auras in their graveyards, the player whose turn it is announces what his or her Auras will enchant, then each other player in turn order does the same, then all artifacts and enchantments (including both Auras and non-Auras) enter the battlefield at the same time.

An Aura put onto the battlefield this way can't enchant an artifact or enchantment that's also being put onto the battlefield with Open the Vaults.

If an Aura can be returned to the battlefield with Open the Vaults, it must be, even if its owner doesn't like what it would enchant.

Any abilities that trigger during the resolution of Open the Vaults will wait to be put onto the stack until Open the Vaults finishes resolving. The player whose turn it is will put all of his or her triggered abilities on the stack in any order, then each other player in turn order will do the same. (The last ability put on the stack will be the first one that resolves.)