The Isle of the Kings is a small island, located in the sea south of the Ghostlands near Carlin and northwest of Greenshore. Some say that monks took over this island to have a peaceful place to read and study their books and the Tibian history, that is true but the island is really for burying the old leaders of the Thaian empire.
There is a big mansion on the island. On the first floor you will find a monkNPC named Costello. You can also find the entrance to the deep dungeons. A dangerous place where only brave adventurers should tread. In this dungeon Fugio - Costello's brother got lost doing some investigation, and to enter, talk with Costello, because he is interested in finding him. Second floor holds the Isle of the Kings Library. Here you will be able to read many books about Tibia, its history, stories and other things. Please do not steal from the library!
The third floor holds the restricted area. This floor is only for the monks themselves and trespassing will be severely punished! If you still enter you need to pay a sacrifice of a certain amount of gold, depending on your level. Anyone below level 20 will have to pay 500 gp, under level 40 you'll have to pay 1,000 gp, level 60 and under pays 5,000 gp, and anyone over level 60 will have to pay 10,000 gp. To do this go with your money to the abbot and say crime.
Accessing the Isle
Since the island is used by the monks to read and study in peace they don't want many visitors disturbing them. The easiest way to get there is to become friends with Dalbrect (here), the man who brings food and wares to the monks. You can find Dalbrect near his boat, north of the Ghostlands.
The other way to come there is to follow the way of the Banshee Quest, then go up near the pearl seal.