The Yokai is a mystical spell-caster that summons the seven sin beasts to cause ruin and destruction. It has generally high attributes, especially in the magic department, with Vitality being its only mediocre stat. It's also a katana expert, which is rather odd considering its stats.
As the final job you can acquire, the Yokai doesn't disappoint. Its Awakening ability allows characters to reach Level 11 in a job, acquiring that job's ultimate ability. But to unlock the Yokai's potential, you'll need to defeat the seven sin beasts--all of which are tougher than the final boss.
After the user casts a spell, there is a 25% chance of casting the same spell a second time without expending MP or BP.
Not a reliable ability, but it's free and provides a nice way to occasionally boost your damage output. Best used with strategies that involve casting multiple spells.
Level 1: Diabolism Level 1
|Command||Lust: 20 MP Thundaja: 99 MP|
Lust has a 50% chance of charming all foes. It's about as effective as the Catmancer's Catnap for stopping enemy mobs.
Thundaja is the ultimate lightning spell, dealing impressive damage to all foes and cannot be reflected. The cost is pretty hefty, but this problem can be resolved by using the Red Mage's MP Free in a Pinch as a ghost.
Level 2: Awakening
This reason alone makes the Yokai worth training, at least until Level 2. Many of the Level 11 abilities are very useful to have and some are even potentially game-breaking (in a good way).
Level 3: Diabolism Level 2
|Command||Gluttony: 20 MP Acid Breath: 2 BP|
Gluttony places all allies in the gluttony state for 6 turns. In this state, damage heals the character instead, but once the accumulated HP recovery exceeds the character's maximum HP, they get KO'd. HP recovery overrides Winter Storm.
This ability is another that's better in the hands of the enemy. However if your characters are able to tank hits normally, this can be used to make them invincible for 6 turns. By the way, don't heal yourself either, as that can lead to a KO as well.
Acid Breath deals 2 times physical damage to all foes and drops their Physical Defence and Magical Defence by 75% if the attack hits. Best used if there are 2 or more foes on the field or if you're up against a foe with sky-high defence buffs. Purgation is better for the latter though.
Level 4: Diabolism Level 3
|Command||Avarice: 3 BP Blizzaja: 99 MP|
Avarice steals 1 BP from all foes (if the foes are undead, you lose 1 BP for each foe). Doesn't work on bosses or similar foes, which is a shame; otherwise, it's a great way to immobilise mobs. If you don't want to waste BP, you should use this when there are 3 or more foes.
Blizzaja is the ultimate water spell, which equates to another deadly asset for your Yokai.
Level 5: Diabolism Level 4
Sloth dispels all buffs and supportive effects (just like the Exorcist's Purgation) from all foes and makes all foes weak to all elements. The cost is high, but once again a trifle for a ghost. Now your Yokai's spells will be even more devastating!
Firaja is the ultimate fire spell, even outperforming the Black Mage's ultimate spell, Flare. Poor, poor Black Mages...
Level 6: Diabolism Level 5
|Command||Wrath: 20 MP Three Blades: 2 BP|
Wrath has a 75% chance of inflicting Berserk to each enemy. Doing so will boost the enemy's Physical Attack, but restrict them to normal attacks. A good way to stop enemies from using their abilities, but can backfire if you're not careful.
Three Blades is an attack on all foes that has a 50% chance of inflicting damage equal to half the enemy's current HP. This is basically the Time Mage's Gravity, but it's physical-based and targets all foes without the need for Spellcraft or Group-Cast All. It's BP-intensive though.
Level 7: Echo
This ability was nice when it was free, but it's too expensive for such an unreliable ability. If you want to use Echo, you should be a Yokai and then you'll have space for superior abilities like the Red Mage's Chainspell.
Level 8: Diabolism Level 6
|Command||Envy: 99 MP Consume Life: 2 BP|
Envy dispels all buffs and supportive effects from all foes and reduces their Physical Attack, Physical Defence, Magical Attack and Magical Defence by 25% for 4 turns. This is very similar to Sloth, but cripples the enemy's offensive capabilities.
Consume Life triggers 4 hits on random foes, each inflicting normal damage, with a 50% chance of KOing the foe (ineffective against bosses etc.). This is a stronger, but more expensive version of the Catmancer's Death Spiral. Still great fun to use against unsuspecting mobs...
Level 9: Diabolism Level 7
Pride dispels all buffs and supportive effects from all foes, while increasing all allies' Physical Attack, Physical Defence, Magical Attack and Magical Defence by 25% for four turns. This is like Envy, but it buffs your party instead. Not as useful since there are many other ways to buff your party, but it's nice.
Aeroja is the ultimate wind spell, completing the circle. Between Thundaja, Blizzaja, Firaja and Aeroja, your Yokai can cover more than half of the common weaknesses by themselves.
Level 10: Obliterate
So long as your Yokai is high level enough, this makes grinding largely devoid of effort, beyond running around with encounters set to maximum. You can't chain battles this way, but the sheer ease of use generally outweighs this disadvantage.
Level 11: Diabolism Level 8
The user assumes the appearance of another ally, enabling them to use the ally's assigned command abilities. At any time, the user may use Reveal Self to return to normal. If Bravely Second is active, the user cannot act while disguised.
This is a neat way to use another ally's abilities without sacrificing a character like the Guardian does. Similar to the Guardian's Possession, the user cannot use Spellcraft or Tongues unless the user has the relevant abilities equipped.