Besieged
Besieged is a new type of gameplay that was introduced to Final Fantasy XI (FFXI) with the expansion pack Treasures of Aht Urhgan. Basically, in Besieged you defend the city of Al Zahbi against an army of beastmen.
The Empire of Aht Urhgan is constantly at war with three groups of beastmen: the Undead Swarm, the Troll Mercanaries and the Mamool Ja Savages. All four groups want possession of one thing: the Astral Candescence. If the Candescence is in the hands of Aht Urhgan, the beastmen groups will build armies and attack the city of Al Zahbi to get it back. When they do, a Besieged occurs.
In Besieged, all players in the area are called upon to fight the beastmen. The city isn't safe for anyone during Besieged. In addition to players, various NPCs join the fight, including the city's own Immortals, as well as goblin mercenaries who fight with you.
Besieged Rewards
In Besieged, there are a rewards that you will receive if you participate, and have Imperial Sanction on during the Besieged battle. Once a Besieged is won, all participants (everyone in the area with Sanction on) will receive an increase in their Imperial Standing, as well as some experience points. How many experience points you get depends on how active you were in the battle. (If you die early and are dead most of the time, you'll receive less. If you're dead at the end, it seems you receive none.) The maximum EXP you can receive is 700. These rewards are relatively small, but there's more to Besieged than just that.
Besieged: The Big Picture
The main purpose of Besieged is to defend the Astral Candescence. The true nature of this treasure is a bit of a mystery, but there is one obvious benefit to keeping it in Al Zahbi. When the Astral Candescence is in Aht Urhgan's hands, you get bonus experience points when you have Imperial Sanction on. This makes gaining experience points (EXP) and levelling in the Aht Urhgan areas faster. The more Besieged events that are won, the higher the EXP bonus. If the Astral Candescence is taken, it drops down to zero.
In addition to experience points bonuses, something else can be lost in Besieged: NPCs. Even if you win Besieged, the beastmen can still abduct NPCs from Al Zahbi. The Auction House NPCs, the Warp Tarutaru (the NPC that will warp anyone to Jeuno, or somewhere near it), quest NPCs, etc. They can all be taken, and if they are, quests, missions and activites that need them become impossible.
If an NPC is taken prisonner, it's neccessary to take a party/alliance into the beastmen's stronghold to recover them.
The Risks
The only risks in Besieged are the loss of the Astral Candescence (and the exp bonus) and the abduction of important NPCs. If you die in Besieged, however, you won't lose any experience points (but you will miss out on some of the end rewards, so get up fast!).
So, it seems Besieged is pretty important if you want to take part in the new areas of Aht Urhgan, gain faster EXP or participate in new quests.
Imperial Sanction
To benefit from Beseiged rewards, you need to have Imperial Sanction. You may receive Imperial Sanction from Immortal guards at the gates in Al Zahbi, but you must be on Treasures Mission 3. (See Aht Urhgan Missions).
