In the upcoming version update, we will be introducing the Nyzul Isle Assault area.
The Nyzul Isle Assault area will challenge players with a dungeon that has a randomly generated layout--every floor will contain new opponents to battle, as well as new objectives to complete!

Development Concept

In the spirit of the Salvage area implemented in the December version update, we will be introducing more small-group content in the form of a randomly generated Assault area. In order to reach the highest level of this new

Assault area, players will have to overcome various mechanisms and monsters, and contend with all manner of astonishing challenges.
The development team is hard at work creating new content that will provide fresh, ever-changing enjoyment.

Participation

Players can sign up for the new Assault area missions at the Commissions Agency in Aht Urhgan Whitegate. Participation is restricted to the usual 3 to 6 members; however, players cannot choose to impose a level restriction for Nyzul Isle Assault missions. There are no requirements for participating in Nyzul Isle Assault missions other than being a registered mercenary.

Assault Mission Progression

The Nyzul Isle Assault area will be randomly generated as a series of "floors" every time you begin a mission. The basic progression consists of working towards the highest level of the area by completing the objective of each floor within the time limit. Objectives include goals such as the defeat of all monsters on a floor, the elimination of specific creatures, as well as various other challenges. We estimate that approximately 5 floors will be completed during a single attempt.

Recording Progress

When using the Rune of Transfer to exit the Nyzul Isle Assault area, it is possible to record the data of the highest floor you have reached (in blocks of 5 floors). Once this data has been recorded, you will be able to start again from this point, even if you have been ejected from the area due to, for example, an expired time limit.
Starting from a recorded floor will require the use of "tokens" obtained within the Nyzul Isle Assault area. The further you progress, the more tokens you will need to begin the next block of floors. Players will require a substantial number of tokens in order to reach the highest floor of Nyzul Isle.
*All participants will obtain tokens from a mission; however, only the person who operates the Rune of Transfer on the starting floor will receive the recorded data.

Rewards

Due to the special nature of Nyzul Isle, players will not receive Assault Points for missions completed in this area. However, you will have the chance to obtain items from the creatures that appear on each floor. Monsters from every corner of Vana?diel, including many powerful and ordinarily elusive Notorious Monsters, stalk the floors of Nyzul Isle. Triumph over these opponents and you may earn some truly rare and wonderful treasures!

source: http://www.playonline.com/pcd/topics/ff11us/detail/1502/detail.html