PvP
From Blade & Soul Wiki
PvP will be a choice option supported by a Flag system, which is manipulated by the use of Doboks.
By donning a Dobok, a player goes into a PvP status known as "Flagged." Your character name changes to red as well as the names of other players wearing the Dobok of different factions. You will not be able to attack players whose names are not red, and when flagged you will be open to attack by any flagged players not in your faction.