We decided to do this last night. It is very similar to most other AF1 quests.
Getting to Arrapago Reef was porbably the hardest part because avoiding those little parasites and imps are almost impossible, but we made it
Inside Arrapago Reef, make sure you have a Lamia Fang Key or have someone on other side to open door. We made this mistake and it was unfortunate. Lydric had to go all the way around from Staging Point. Go to the ??? on the ship where COR job takes you.
You view a CS, and then chose MAze of Shakrami. Head there and go down to Basement where the Argus NM Scorpion Spawns. There is an Iron door. Simply touch the door and the Lost Soul will spawn. Claq and Lydric fought this (75 PLD and 75 THF) and really seemed to have no problem what so ever. I am guessing it is 65-70. After that click on the door for a CS and return to the reef.
All you have to do then is make it to the Whitegate and talk to Rahib at the Tea House. He is in crafting apron and you are set. Might have to talk to him twice as I did.
Your reward is your AF weapon, the Trump Gun, not too shabby and delay time is much better than most guns. TY for help guys.