VoodooMaster Quest/Spoiler

Go to the West part of the island Goroma, and go into a small secret cave. Loot the dead person for the book, and go back to Liberty Bay.

Then, travel to Meriana ("Peg Leg") island. Go to the voodoo master, most north as it gets, and tell him spellbook. He'll take it. Now, you'll need a dead chicken, a dead rat and a dead black sheep. Best way would be to summon and kill it. Once you got those on you, talk to him about "Counterspell". He'll then cancel the electric wall that was on Goroma, and you can pass there.

Once you get past this wall you will be able to reach cults and then you can go thorough a teleporter to reach all other Foribidden Islands... Ramoa, Malada, Talahu and Kharos