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Mastermind of Discord
25% increased Effect of Heralds on you
Damage penetrates 25% Fire Resistance while affected by Herald of Ash
Damage penetrates 25% Cold Resistance while affected by Herald of Ice
Damage penetrates 25% Lightning Resistance while affected by Herald of Thunder 
Mastermind of Discord is a notable Ascendancy passive skill for the Elementalist that grants elemental penetration based on the element you have a Herald skill active for. It also grants Heralds increased effect and reduced mana reservation.