Cargo Ship to Lindblum
Go to the end of the walkway and up the ladder once you are back in control of Zidane. There are a few scenes on the ship including the one with Vivi and another with Steiner. Enter the bridge to continue the story.
Make sure you steal all of the items that Black Waltz 3 possesses. This could take a fair amount of time as there is only a 6.25% chance of successfully stealing the Silver Gloves. Have Steiner both focus on support with healing spells and Potions.
Vivi starts the battle off in a Trance so use a few magic spells to get the battle rolling. Just make sure that you don’t kill Black Waltz 3 until you have stolen all three items (it has 1,128 HP).
This boss does not counter Vivi’s attacks so you’re free to use as many spells as you can. Have Vivi focus on healing as well with Potions until Zidane has successfully stolen all of the items.
Black Waltz 3 will target all party members with its spells when it rises in the air. You also cannot hit it with standard attacks when it is flying in the air.
A video of the battle is included below:
There are a few more scenes that occur after the battle before the team arrives in Lindblum.