Redemption Island is a major twist to the standard Survivor game.
Being the primary twist of Survivor: Sri Lanka, this twist 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 will compete in head-to-head challenges (known as Duels) in order to remain on the island and avoid permanent elimination. The twist returned eight seasons later for Survivor: Eleventh Hour.
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 Redemption Island. When the next person is voted out, that player would be sent to Redemption Island as well, meeting up with current inhabitant at the same night. They would then live together from that point, until the next morning, where they will duel to remain on the island. At a certain point in the game, the person remaining on Redemption Island would re-enter the game in pursuit of the title of 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 winning the final duel, 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 duels 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 inhabitant, he/she can have a longer time to rethink strategy and how he/she will re-assimilate with his/her former comrades. The "resurrected" player may forgive the same people who double-crossed him/her, or might show bitterness by making bolder and more rebellious moves, to avenge his/her untimely departure, such as creating a counter-alliance with the rival tribe, though all rethinking may all be wasted if they lose a duel. 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.