Zero Isle South is a dungeon in Pokémon Mystery Dungeon: Explorers of Time, Darkness, and Sky, and it is considered the ultimate dungeon of the games, along with Destiny Tower in Explorers of Sky. As with Rescue Team's Purity Forest , the player is reduced to level 1, lose all items and money upon entry, and must travel alone with no enemy Pokemon joining the team. This means that victory relies mainly on the luck that the right items appear at the right times.
Just as with the other Zero Isle dungeons, Zero Isle South has locked chambers containing exclusive items for legendary Pokemon and/or rare, useful items. The locked chambers are located on floors 15, 25, 30, and 96. However, only the first two locked chambers have a chance of containing a box with an exclusive item for a legendary Pokemon (the item in the box will be exclusive for Celebi, Jirachi, or Dialga for the first chamber and Raikou, Entei, Suicune, or Ho-oh for the second chamber). Therefore, returning to Zero Isle South is necessary if one wishes to collect the exclusive items of all the legendary Pokemon in the games. The reward for making it to the end of the dungeon is a Deluxe Box with either a Life Seed or a Joy Seed, as well as being able to fill an entry of your adventure log if you have explored the other three (four for Sky) Zero Isle dungeons.