Dual Raid Party Quest
You need to be between Level 60 to 80 (inclusive) to do this competitive party quest, which is also known as the "Ghost Ship in the Sea Mist Party Quest".
In order to enter this PQ, it is necessary for the party to be consisted of exactly 3 members. There are no pre-requisite quests that you need to do in order to participate in this PQ.
You can access the PQ either through:
1) 
Mirror of Dimension, which is located at nearly every town, or
2) 
Dolphin at Aquarium or Herb Town: Pier on the Beach.
The party leader should talk to 
Norington to either create your own room or join another party's room.
It's a good idea to complete the Strategy Rooms as quickly as you can, as the fastest team that does so will net a -5% handicap from the Boss' HP.
Foggy Ocean: Strategy Room 1
Kill every single 
Private First Class Ghost in this room. That's all there is to it.
Foggy Ocean: Strategy Room 2
You will firstly have to hit 7 
Wooden Box to summon 
Corporal Ghost for you to kill.
Foggy Ocean: Strategy Room 3
Defeat 
Top Officer.
Be forewarned that it can summon Private First Class Ghost, Corporal Ghost, and 
Sergeant Ghost.
Foggy Ocean: Strategy Room 4
Kill all Sergeant Ghost and 
Staff Sergeant Ghost.
Be forewarned that Staff Sergeant Ghost can darken the entire map except for the small area around your character.
Foggy Ocean: Strategy Room 5
Attack the red lever, then run straight for the spring and jump on top of it, and you will be brought to the other side of the lake. Once there, defeat the Staff Sergeant Ghost and 
Sergeant Major Ghost that appear.
If you manage to kill all the monsters first, congratulations! The boss in the next room awaits you with 5% less HP. On the other hand, if the opposing party eliminate all the monsters first, any remaining monsters will disappear and you will be sent to the next stage.
Foggy Ocean: Lost Captain Room
There'll be two HP bars for Team Red and Team Blue, and whoever defeats the boss first wins!
Captain of Ghost Ship has a variety of skills and curses that it can inflict on you. The curses include: temporarily disable you from using potions; and casts a skill that damages your character if you don't move.