Sundered is a new(ish) damage effect that can be inflicted by any Martial attack.
Most attack types added a status effect previously (poison, disease, concussed, burning etc etc) but plain old stam-based physical attacks did not. "Sundered" was added to make up for this difference.
Sundered
The Sundered status can be applied by dealing Physical Damage to a character. A sundered enemy suffers from Minor Breach debuff for 4 seconds, decreasing their physical and spell resistance by 2974.
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