Mental Break is one of Steiner'sSword Arts. It halves a target's Magic Defense, costs 8 MP to use, and can be learned for 45 AP from the Ice Brand and Gold Helm. It has a 50% accuracy, but can be used repeatedly.
Shear is a Technick that lowers the target's Magick Resist by 10% and can be used repeatedly. No enemy is immune to it, but it has a fairly low accuracy of only 33%. Shear can be bought in Rabanastre, Nalbina and Jahara for 3,600 gil and it takes 35 LP to unlock on the License Board.
Scale Strip is the level 4 command ability for the Pirate. It allows the user to deal the same damage as a conventional attack to one target, and for four turns, lower the target's M.Def by 25%. The lower limit for M.Def is 75%. It costs 9 MP to use.