The Queen That Was is a sidequest that you can complete in Sea Of Stars. It rewards Serai with her Ultimate Weapon and allows you to collect a hidden Rainbow Conch.
To begin the quest, head down into The Vespertine and speak to Serai. She mentions of an old threat to Repine called The Queen That Was.
She recommends speaking to Teaks for more information. You need to listen to the story The Cerulean Expedition.
Throne Of The Queen That Was
There is a secret pathway within the Cerulean Expanse that allows you to gain access to The Queen That Was.
The story mentions three expeditions and gives clues to the path that you need to follow.
The path is: Northeast, Southeast, East, Northeast.
You'll come to the Speedball Network that takes you to a new area called Throne Of The Queen That Was.
Here you can pick up a Treasure Chest on the right that contains the Artful Gambit relic.
You can also find a Rainbow Conch in the top-left corner.
Head up the stairs to find The Queen That Was.
Gun Goddess - Boss Fight
The Gun Goddess has some new mechanics to be aware of. She will summon her bullets, all of which are resistant to all types of attacks. They don't have a lot of health, but there are 6 of them. They are used in an attack that will deal heavy damage to all three characters called Fan The Shot. If you use multi-target attacks, it will take around 4 of them to take all 6 bullets out.
The gun Goddess regular attack hits all three characters for around 40 HP. It also has a single-target hit that deals around 70 HP.
It's main attack is called The Shot, which will one-hit KO anyone who takes it. You can use B'st to revive, so make sure he has plenty of MP available.
The second main attack it uses is called Fan The Shot; this is where it will use any remaining bullets and fire them at everyone, dealing around 100 HP each. The bullets are not consumed, so it can hit this attack several times.
Make sure you have Resh'an available for healing, Mending Light combo available and in dire situations you can use Valere's Lunar Shield for some small healing.
The boss itself does not have a lot of HP, so we found ignoring the bullets and just focusing on the boss helped clear it quite fast.
Check out the video for more tips:
Reward: 15,200 EXP
After the fight, Serai can pick up her Ultimate Weapon called Star Shards.