Story arc

A story arc (also referred to as Mission Chain) is a series of missions, usually ending in an instance where the main antagonist of the arc is faced. The arc may include different types of missions: killing X ammount of mobs, gathering Y ammount of items, completing one or several instances.

Usually an arc has one or several associated briefings, investigations, feats and headlines.

An example of a story arc is Survival of the Fittest: Episode 1