The Stock Gauge bar is the yellow-green bar found below a character's HP, MP, and SP gauges.
It affects many things in battle, from being able to use Hard Hits, Double Attacks, and setting up Combos and Double-Combos for Combo Magic.
However, the same is also true of enemies, who have their own Stock Gauges.
The Gauge has three levels of Stock; 0,1 and 2.
Succesfully attacking enemies with regular, special, or magical attack will raise the character's Stock. Taking damage from enemies will also build Stock.
However, being attacked by Hard Hitting abilities will reduce the Stock, and several enemies also have moves that can drain Stock.
The Apathy Status renders a character unable to gain Stock, while the Stock Up Status will increase the amount of Stock gained per action.