By Dr Mike
Buy as: A stun attack, possibly with other effects.
Intensity effect: Varies.
If you want an attack that does two types of effect, buy the primary effect you want and add some stun to it. The stun will then be swapped for another effect when the attack lands.
If you want a piercing damage attack that does acid burn (eg a posioned blowdart), buy a piercing attack that has a decent stun chance on it. Then swap stun to acid burn in FFX Control Centre - when the stun takes effect it will be instantly removed and repalced with the acid burn state.
Targets that are resistant to piercing, or have defneces against it will be less likely to be stunned, and therefor less likely to be acid burnt.
Two swaps can apply to the same power. Say you want a Crystallise attack that also causes life drain sometimes, you could buy a hex attack with stun on it, and swap the hex for crystallise and the stun for life drain. If the hex succeeds, then the crystal will form, and the stun chance is checked. If this succeeds, then the target also gets lifedrained.
Note that when adding stun to state attacks with a %age chance of succeeding like this, the primary attack must succeed before the stun (and hence the carrier attack) are checked. Stun on a primary state attack (eg Rage, Freeze) never succeeds.