Equipped for All Occasions

Head to the ??? in Arrapago Reef used in COR Flag Quest: Luck of the Draw.

Examine the ???.

During the cutscene, you will be presented with a 3 choices: Gusgen, Maze of Shakrhami, and Ordelles.

Maze of Shakrhami: -Head to the Iron Door in Argus Spawn area and examine it to spawn Lost Soul.

Gusgen:

Ordelles:

Lost Soul: This NM is not much different than other AF1 NMs. He's a Skeleton and has about 3500 or so hitpoints. When he gets to about 10% hitpoints, he will start to spam Blood Saber. Soloable by some 75 jobs, such as NIN or RDM.

After defeating the Lost Soul, examine the Iron Door again, and you will get a cutscene where you will be awarded a key item.

Bring the key item back to the ??? in Arrapago Reef for another cutscene.

Head to Shararat Teahouse in Aht Urhgan Whitegate.

Wait 1 Vana'diel Day and speak with Rahtib.

You will be presented with Trump Gun.