If a Stormblade is positioned within 3″ of more than one Stormclad, will the closest non-Stormblade model within 4″ suffer a POW 10 chain reaction damage roll from every Stormclad, or just one?
The extra attack does not come from the Stormclad. Rather, if a Stormblade is close enough to a friendly Stormclad, the Stormblades ranged attack arcs to another target. Therefore an attacking Stormblade only benefits from Chain Reaction once regardless of the number of Stormclads in the vicinity.