Three Kingdoms of DeFugel, Croxion and Broa exit within the Continent of Iveria where each Kingdom rules over a number of territories that are composed with several Districts. However, there are number of disputed territories that does not belong to any Kingdoms. 

Within those disputed territories, a castle is built to protect the territory and collects tax from 3 areas(villages) within the territory.

Castles can be owned by a Guild from each Kingdoms through Siege Warfare that only one Guild, gained most points from RvR(Monday ~ Friday), can participate.

The Guild that won over the Castle owns the territory for a week until the next Siege Warfare, and through the Administrator of the Castle, they receive the tax from all the item

trades from all the stores in the territory, and they have right to monopolize all the local-product items. Also, the Guild is allowed to add more guards or equipments for protection to prepare for the next Siege Warfare.

Siege warfare is a war between the Guilds to own a Castle, however, the Warfare has an aspect of a war between Kingdoms. Especially, a Siege Warfare over a territory that is essential for item trades and completing Quests will become a war between the Guild from each Kingdoms fighting for their Guild's and their Kingdom's pride.

Siege Warfare in 4 story gold is not just a war between Guilds but it's a war between Kingdoms that both attacking and defending groups can accept users from their Kingdom to join the war through the mercenary system.

Mercenary System is the system where both attacking and defending Guilds can hire certain users from their Kingdoms to join and fight for the victory.

There are 2 types of mercenary system. User can participate as a Freelance mercenary with their own ability or as a Recruit mercenary team where the users will be equipped with arms, armors and skills 4 story goldthat the Guild provides.