The Isle of the Chosen
In the magical collision that created the island a sort of anti-portal was born. It expanded as a balloon over the island creating a very odd boundary. The few islanders who have tried through any method to leave the island have found that at a certain point though they feel they are still moving the island seems to stay an equal distance from them. The strange occurrence is known to very few, those who are devout simply explain this as the will of the Gods that none of the chosen shall leave the island.