The Cataclysm: Vietnam is the twenty-fifth season of the fictional reality competition series The Cataclysm. It is the third season to feature a mix of new and former players, and it the sixth overall to feature returning players.
Taking place in Sierra Leone, nine men and nine women, compete in the ultimate test of strength, endurance, and intelligence in order to be the "last one standing" and claim the $2,000,000 prize.
Contestants Alison Lawrence, Derek Lara, Kyle Bond, and Malaya Cardi returned for The Ultimate Cataclysm.
- Exemption Challenge: The Cataclysm's immunity challenge. The winners of this challenge are exempt from elimination.
- Commander: Prior to an exemption challenge during the faction stage, each team must select a member to be the team captain. This player becomes the Commander for that challenge. The Commander of the winning faction gets to nominate three players from the opposite team to face the voting ballot.
- Ballot: The Cataclysm's elimination round. Those nominated to face the ballot risk being eliminated.
- Medallions: Three medallions are eligible to use in the game: the Resurrection Medallion, the Chaos Medallion, and the Fire Medallion. Contestants must solve clues to be able to find these medallions.
- New Players vs Returning Players: The initial factions are divided based on new players, players who have played once previously, and players who have played twice previously.
|WINNER||The contestant won The Cataclysm.|
|Runner-Up||The contestant finished in 2nd place.|
|2nd Runner-Up||The contestant finished in 3rd place.|
|WIN||The contestant won the Exemption Challenge as the Commander (Faction Stage), and nominated three opposing players for the voting ballot.|
|WIN||The contestant won the Exemption Challenge and was immune from elimination.|
|SAFE||The contestant was not immune, but was not placed in the ballot.|
|LOW||The contestant faced the voting ballot and survived.|
|BTM||The contestant faced the voting ballot and received the second highest number of votes.|
|ELIM||The contestant received the highest number of votes and was subsequently eliminated.|
- On Episode 4, Sasha played the Chaos Medallion, thus adding April into the ballot as well.
- On Episode 6, Malaya broke the tie between Aubrey and Paula in the voting ballot.
- On Episode 10, Liam played the Chaos Medallion, thus adding everyone into the voting ballot.
- On Episode 12, Alison played the Resurrection Medallion on herself and removed herself from the voting ballot. Also, Kyle played the Fire Medallion and used it to nominate Aubrey for the voting ballot.
- On Episode 13, Sasha played the Resurrection Medallion on herself and removed her name from the voting ballot.