You are back with Sazh and Vanille and should have some CP to invest. For Sazh, unlock Boon (Synergist), Scourge and Jeopardize (Commando) then aim for the Commando role level. Vanille should aim for Renew and Raise then the Medic role level. Create the Undermine (RAV & SAB) Paradigm then set off to make your escape.

This area is full of bulkhead doors that can be opened by switches outside of them. Flanitors are nothing but a mere annoyance at this stage but Flanborgs can be more tricky; use Undermine to Stagger them quickly. Dispatch the first group of enemies and approach the switch to open the door.

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Flanborg enemy (left) and Royal Armlet location (right).

When you reach the split path, take the right-hand one, open the door, kill the enemies inside and claim the Royal Armlet from the Treasure Sphere. Just before the waypoint, pick up 12x Murky Ooze then proceed forwards.