Occultus Island is a major twist to the standard Survivor game, based upon it's predecessor Redemption Island.
Being the primary twist of Survivor: Occultus Island and Survivor: Japan, this twist, like Redemption Island, provides an opportunity for an eliminated player to re-enter the game and continue their pursuit for the title of Sole Survivor. In order to do so however, eliminated contestants have to compete in a condensed version of the post-merge Survivor game, with Individual Immunity Challenges and Tribal Councils. Those voted out of an Occultus Island Tribal are permanently eliminated from the game.
Immediately after being voted out, the castaway would take their snuffed torch with them as they walk out from the Tribal Council set. Then they would be instructed to go to Occultus Island. When the next person is voted out, that player would be sent to Occultus Island as well, meeting up with current inhabitant at the same night. When five people are on Occultus Island, the process begins. Individual Immunity Challenges are the only way of staying safe from Occultus Tribal Councils. If you are voted out of an Occultus Island Tribal, you are out of the game permanently. Once someone is voted out of Occultus Island, their space is filled by a new player - the most recent person voted out of the main game - and the cycle continues. At a set point in the game, a certain amount of people remaining on Occultus Island return to the game after a final battle for another chance to become the Sole Survivor.
For the remaining contestants, eliminating other players would be a more difficult burden. Given that they would be voted out from their tribe, chances are that player they chose to vote may come back. In theory, if a player was removed from a tribe after a blindside vote, and returns after surviving the Island, a more unpredictable series of events would complicate the game. For instance, voting out a physically strong player can be potentially risky, as that player might win subsequent Individual Challenges and will just come back on a later time. Also, if the contestants are chosen as observers, any divulging of the goings-on at their camps is potentially fatal, because this will be substantial to the strategies of the returnee, and worse, to the rival tribe.
As for the Island's current inhabitants, they can have a longer time to rethink strategy and how they will re-assimilate with their former comrades. The players may forgive the same people who double-crossed them, or might show bitterness by making bolder and more rebellious moves, to avenge their untimely departure, such as creating a counter-alliance with the rival tribe or with the others on Occultus Island, though all rethinking may all be wasted if they get voted out again on Occultus Island. Furthermore, re-assimilating back into the game will be difficult because the inhabitant is oblivious to the happenings at the tribe camps. Additionally, a "resurrected" player is not guaranteed free immunity, making him or her vulnerable from getting voted out once again, so winning immunity is crucial.