You’ve learn how to combo effectively with other allies.
Prerequisite(s): Combo Finisher class feature.
If you use a combo finisher on an enemy that has also been hit by a combo finisher by an ally within 30 feet that also has this feat in the same round and both attacks used the same amount of weapon dice (such as triple weapon damage or martial damage) you deal additional damage equal to your double weapon or martial damage to the target. This can happen on multiple targets if they have been hit by a combo finisher that also hits multiple targets as long as the amount of weapon damage matches. A combo burst can only happen once per round per target and happens immediately when it can. The window for a combo burst lasts until for 1 round after the first combo finisher is used.