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.
Wonder if they'll ever stop writing events with the usual "oh I'm such a sad, unfortunate and forge...