There are factors that play in chances of success for skills that "purge" enemies, or remove them from battle without killing them.
The six ones used (or the only ones i can currently think of) are Exorcise, Burial, Parley, Wyrmtamer, Oust, and Capture.

Exorcise/Burial
They are learned by White Monks and Archers, respectively. These skills only purge the undead and, actually have no special formula for it. It's just a low percentage.

Parley/Wyrmtamer/Oust
They are learned by Paladins, Dragoons and Hunters, respectively. These skills each deal with a certain job or class. Parley works only on humans, Oust works only on animals, and Wyrmtamer works only on dragons. (Why did they even put Wyrmtamer in ffta- it seems useless compared to Oust but whatever.) The formula for these are:

MinHP%: 50-KO's the caster has made
HP%: Target's MaxHP * MinHP% / 100
HitRate%: HP% - Target's HP * 100 / HP%

Capture
It is learned by Hunters. This is comparable to Oust except that not only is the formula different, but the monster removed from battle is yours to keep and goes to the monster bank in Cyril. You can use the soul given from the capture and give it to a Morpher to learn that animal's skills. Also, feeding the animals in the monster bank will boost their stats to the Morpher and give it high power. Try elixirs and/or curealls, they really work wonders. The formula for Capture is:

HitRate%: Target's MaxHP - Target's HP / 4

There are many other factors to go through before it will even work in the first place:
1) The monster cannot be at full health
2) It cannot be the last one remaining (I'm not sure if Petrifying counts as a KO, gotta try it)
3) You cannot capture two of the same monster SPECIES. For example, you can't have 2 ice flans, but you can have one ice and one fire.
4) If it has a hero medal (that medal that let's units violate as many laws as they want without getting a red card and nullifying some status ailments) then it cannot be captured.
5) The following monsters cannot be captured: Undead, Fairies, Rockbeasts, and Tonberrykind.






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By the looks of this, if the character has killed more than 50 people the move wont hit... can u work it out with an actual number for the parley/oust moves

suwtic :
Example Time! (Queue ffta wind symphony)

let's say a character has killed 25 people, and the target's MaxHP is 420, and they're at their lowest HP possible (1).
MinHP%: 50-25 = 25
HP%: 420 * 25% / 100 = 105 / 100 = 1.05 (we multiply by percent)
HitRate%: (1.05 - 1) * 100 / 1.05 = 0.05 * 100 / 1.05 = 5 / 1.05 = 5 rounding up (we don't subtract by percent, only the number)

So that's 5% it will work provided the conditions We regard the percentages like I've stated above because if we do it the opposite ways, then the percentages end up being above 100% and that's impossible, the highest percent you can achieve is 90 because the monster's HP has to be less than half.

This is confusing me

MinHP%: 50-KO's the caster has made

if the caster has made 50+ kills the % would be zero or negative wouldn't it

suwtic :
Exactly. So basically you need a newb on your team to use the skill, or they'd have to be someone that barely kills people like a White Mage or any job that uses petrify instead of KO

well that seems highly pointless, considering you could kill most of the enemies in 4-5 turns

Which is why i only use the hunter because he never kills for me he just captures