Guild Wars: State of the Game @ Official Site

The latest State of the Game article at the official Guild Wars site takes a closer look at the use of NPCs on the battlefield.

Non-player characters (NPCs) play a vital role in any Guild-versus-Guild combat. Teams use them to gain an offensive advantage over opponents, or use them defensively to make a stand and regroup after a setback. In an otherwise balanced fight, smart use of computer-controlled allies could give you that slight edge you need to overwhelm the opposition.

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Source: Guild Wars