Diablo 3 patch 2.6: Necromancer set: Jesseth Arms
This is a 2-piece Necromancer set added in 2.6.0 buffing minion's damage.
(2) Set:
When the target of your Command Skeletons dies, your skeletons are automatically commanded to attack a nearby target.
While your skeletons are commanded to attack a target, all of your minions deal 400% increased damage.
Cast Command Skeleton once, skeletons automatically rush to mobs one by one until all nearby mobs are dead. What more important is as long as the Command Skeleton debuff is on, all your minions deal 400% more damage. Therefore, makes sure the debuff is on all the time, which is indicated by the bright light covering your skeletons.