When Starfrost Swirl's Flowfrost Arrow first hits an opponent, or its Rimestar Flare hits an opponent, 1 Detector stack from Passive Talent "Suppressive Barrage" will be generated. You must have unlocked the Passive Talent "Suppressive Barrage" first.
Correction to point 3, Clorinde's burst Mace's itself as C4 since she gains the maximum boost at 10...