Requirements
Method
Mission 1
Make your way to Alexander at the Edron Academy (third floor) and ask him about a 'mission'
Alexander will let you know he needs to bless you with fire protection before you can sail to the island. To do so, he requires 1x Bowl, 1x Bird Beak, 5x Green Dragon Leather and 10x Fire Mushroom.
After handing over the items, Alexander will prepare and cast the blessing on you: "You have received a protective fire blessing."
You can now sail to Kastah with Captain Seahorse for 450 gold.
Mission 2
Find Kafer at the magic shop (second floor) in Kastah, located directly south of depot.
Ask Kafer for a 'mission'. He will let you know the island has had problems with bringing in shipments and asks you to aid him with establishing a strong magnetic force to help guide the ships.
He asks you to seek out a central location of the island suitable for a strong magnetic force. Make your way out of the east-gate of Kastah and follow the route below:
As you arrive to the old outpost, go downstairs into the basement and you will see the following message:
Head back to Kafer and report your finding by telling him 'mission'.
Mission 3
For this mission you need the Iron Hammer. It can be obtained from Iron Hammer Quest in Kazordoon.
Once you have the hammer, talk to Kafer about a mission and he will transform the Iron Hammer into a Magnetized Iron Hammer.
Head back to the old outpost and use the Magnetized Iron Hammer on the blue stone in the basement.
Go back to Kafer and tell him 'mission'.
Once you are done with this mission you can start tasks from Commander Kruge.
Mission 4
Now that a new magnetic force is established, you need to go to Ankrahmun, Darashia and Edron and tell the captains to sail towards the correct bearing.
After completing the dialog with each captain, they will allow you to sail to Kastah cheaper.
Use this dialog for the respective captain:
Ankrahmun - Captain Sinbeard: 'bearing', '22'
Edron - Captain Seahorse: 'bearing', '135
Darashia - Petros: 'bearing', '67'