In order to participate in assault, a player must have the Treasures of Aht Urhgan expansion, have completed the quest to go to Whitegate, and successfully become a mercenary for the Empire. The mission to become a mercenary involves traveling to at least one of the staging points. There are five staging points and players can only do assault missions for the staging points that they have visited.
Most missions have a certain requirement for the minimum and maximum number of players needed to do the mission. With little exception, the minimum amount is 3 and the maximum amount is 6. Players must be of a specific level in order to undertake the event. No assault missions are available to characters with levels less than 50. Some missions may require the player to be even higher than level 50.
On the other hand, there is an option to cap the maximum level of a player while inside an assault. While under a level cap, the player's maximum HP, MP, and abilities are limited to what he would have at that level. These level caps are at levels divisible by five, but not available for just any mission. A player will also lose experience relative to his capped level, rather than his actual level should he die. No experience or level is lost simply by virtue of accepting a level restriction.
In order to participate in Assault, a player must have a tag that marks them as a mercenary in the hire of the Empire. One tag is issued per day. Up to three tags will be available at the desk at any one point if the player has not picked up a tag within the last 3 days. The player can always hold onto one tag. It is a key item, so it will not hold up inventory.