From the game's website:
The world of Lineage II is a war-torn land spanning two continents, where trust and betrayal clash as three kingdoms vie for power. The young king Raoul has successfully quenched a civil war and established the newest kingdom, Aden. Elmore, the military superpower located in the northern part of the continent, boasts that it is a direct descendent of ancient Elmoreden kingdom. Gracia, located across the ocean on the west, is currently embroiled in a chaotic battle among blood relatives trying to take over the throne. These kingdoms share a delicate balance of power; however, within each kingdom they are vulnerable to internal strife, as each manor has strong desire for self-rule.
You have been thrown into this chaos. However, unlike the ordinary people who pray each day for safety, you have the power to protect yourself. In Lineage II, developing a character is not an end in itself. Rather, it is your instrument to obtain the power to enforce your will in this world. Seize your destiny! Your own hand will write the history of this world.