Dark Knight: Guide by Raenryong/Magic

Magic
Dark Knight is, strictly speaking, a melee with a little bit of magic on the side. It is not a melee Black Mage, strictly speaking.

We only have three natural magical skills, and only two are really useful.

Dark Magic
Magic Grade: A- Notable Spells: Drain, Aspir, Stun, Absorb-TP, Drain II, Dread Spikes
 * Advantages
 * Highest natural Dark Magic in the game, along with Black Mages, and the best Dark Magics in the game.
 * Drain is an incredibly efficient nuke in terms of damage:MP ratio.
 * Aspir is a very good way of keeping your MP high, and very inexpensive (10MP).
 * Absorb-TP, when used well can make your TP gain a lot faster.
 * Drain II is good for preparing for a zerg (higher HP = higher Souleater damage) and also to mitigate AoE damage. It's also fairly strong.
 * Dread Spikes is a powerful damage mitigation ability.
 * Stun is an essential spell and in my opinion, one of the best spells in the game. It is incredibly helpful in just about any situation.
 * A lot of equipment enhances Dark Magic skill, allowing you to boost your Dark Magic easily.
 * Dark Seal, a merit ability, enhances the next spell; handy for something like Drain II on a more resistant adversary.
 * Most spells have a low MP cost, perfect for Dark Knight's low MP pool.
 * Disadvantages
 * The damage of Dark Magic is very volatile.
 * Except for Stun, useless on undead or dark-type foes such as bats.
 * Aspir can only be used on foes with MP.
 * When casting magic, you are not swinging your weapon, generating no TP (unless of course you are casting Absorb-TP).

Notes: This may seem initially hard to keep capped, but it will become very simple when you get Stun. Absorb-AGI and Absorb-VIT have uses if the mob lasts long enough for their effect to be noticable; personally, I cycled these up until level 65 or so on any mob that checked as IT, although there is debate as to whether it is actually worth it. The general consensus is that they are definitely not useful in a situation where the mobs die fast (which is exp parties after a certain point).

Notes on Absorb-TP: It is best to use this when the mob has a lot of TP; ie, not immediately after it uses a TP move. It is sometimes possible to Stun and very quickly Absorb-TP afterwards. It is also best to try to only Absorb-TP if your TP is below 70 to be efficient; it is largely situational.

Further information on use of Stun will be detailed later, since it is such an essential and versatile spell.

Elemental Magic
Magic Grade: B+ Notable Spells: None
 * Advantages
 * Fairly useful in the early levels for performing a magic burst.
 * Disadvantages
 * No Magic Attack Bonus means nukes are lacking in power.
 * High MP cost on nukes negate any value they could have due to the limited nature of Dark Knight's MP pool.
 * When casting magic, you are not swinging your weapon, generating no TP.

Notes: This is purely for very early game use. Dark Knight does not have the Job Abilities, Job Traits, MP pool, or the magic selection to make this a powerful force. Keeping it capped is more for the sake of a blue number than for any actual benefit.

Enfeebling Magic
Magic Grade: C Notable Spells: Sleep, Sleep II
 * Advantages
 * Keeping a mob slept is an invaluable asset.
 * Disadvantages
 * Low Enfeebling Magic skill means that your sleeps are largely unreliable.
 * When casting magic, you are not swinging your weapon, generating no TP.

Notes: The easiest way to cap this skill is to sub a job which gives you access to Dia: this is nearly unresistable and so will build your skill fast. This is more of a solo skill than anything, but it is VERY handy.