Final Fantasy X has a rather unique character system that potentially allows any character in the game to learn any skill or spell in the game. Characters that are more naturally suited towards certain skills and spells are designed to learn those skills and spells more quickly, but if you play your cards right, any character can learn any skill or spell as easily, or sometimes even more easily, than the character designed to learn those abilities. All abilities are separated in four categories: white magic, black magic, skills, and special skills. Black magic costs magic points to use and is primarily focused on injuring and hindering the enemy. There are a few black magic spells that can also help the caster, but at the cost of the target. The following guide to black magic in Final Fantasy X will help you decide which spells are worth getting and for which characters.
Fire / Thunder / Water / Blizzard – These four spells are easily available to Lulu at the start of the game, though you do have back track a little bit in order to actually learn all four. While they are cheap to cast, they also deal relatively low damage. You don’t have a massive need for direct damage black magic spells in the early part of the game, since physical attacks are nearly as useful. If you want to save some Ability Spheres and a little AP, skip all four spells and make a straight rush for the next tier of damage spells. This basically means that you won’t use Lulu at all in the early portions of the game. Alternatively, by spending four easily gained Level 1 Key Spheres, you can actually give all four of these abilities to Wakka and Rikku at minimal cost.
Fira / Thundara / Watera / Blizzara – In terms of both damage and magic point cost, these spells are pretty much the bread and butter of Lulu. If you are going to use a Teleport Sphere to teach anyone black magic, these are the best four spells to learn. Yuna, in particular, should use a Teleport Sphere to learn these spells as soon as Lulu has unlocked all four. This will give her an effective attack option other than summoning. You should stock up on extra Ethers and use these spells liberally. Treat these spells like they don’t have a cost and use them as often as normal attacks.
Firaga / Thundaga / Waterga / Blizzaga – Wakka has easy access to these four spells if you are willing to spend a Level 2 Key Sphere. In fact, if you pretty much don’t upgrade Lulu at all during early levels, you can have Wakka move into this section of the Sphere Grid, teleport Lulu there, and only have her ever use this tier of attack spells. When you finally get access, you should never use any of the previous spells again, but it won’t be until late in the game that you get access unless you use that Key Sphere. The one downside of these spells is that by the time you get them, there are other tricks you can use to deal damage more effectively. If you are running low on Ability Spheres, consider only learning one and simply making a dash towards Flare after that.
Flare – This is, by far, the best black magic damage spell in the game. Wakka can unlock a quick route to this spell with a Level 3 Key Sphere, but you generally have better ways to use those spheres. Instead, just send Lulu to it as fast as possible and have Yuna use a Black Magic Sphere to learn the spell as well once Lulu learns it. Since the spell doesn’t deal elemental damage, it always deals full damage to the target. You will burn through magic points using it, but by the time you learn it Ethers are dirt cheap.
Bio – No character gets to this spell quickly, which is a shame, since it is rather useful. Wakka can unlock a backdoor route to it with a Level 2 Key Sphere, but he needs to back track away from Firaga in order to get there. Lulu will simply walk over it naturally while moving between Fira and Firaga. The usefulness of this spell comes from boss battles. Use it early in a boss battle and you will deal a massive amount of damage over time. In fact, the damage you deal is higher than you can expect from any other damage spell except maybe Flare, and at a much cheaper cost. You really only need one character to know this spell, so let Lulu learn it and don’t worry about your other characters.
Demi – Demi is found on a route that stops at a Level 4 locked sphere, just before the lock. If you really want to spend four Level 4 Key Spheres and a Level 3 Key Sphere, you could continue to follow that route to the Doublecast skill, but you can also get to that skill by spending only a single Level 4 Key Sphere and a Level 3 Key Sphere once you have followed the path past Thundaga. Effectively, that makes Demi a dead end. And the spell isn’t that good for one at a dead end. It will reduce by ¼ the current health of all enemies, assuming the enemies aren’t immune to the spell. Many enemies are immune. Also, this spell can never kill an enemy. Since there is a hard limit on the damage you can deal with any attack, this spell is worthless against the enemies that it should be the most useful against, those with hundreds of thousands of hit points. Generally it isn’t worth the effort to acquire.
Death – Death is at the end of a dead end route on the Sphere Grid just before you reach Waterga. Like the Death spell in almost every previous Final Fantasy game, the majority of enemies in the game are immune or resistant to it. Spending magic points on a spell that is more likely than not to do absolutely nothing, is really just a waste. You should skip this side path in order to speed up your route towards Flare.
Drain – Drain is a rare spell that is basically useful for all characters. It doesn’t deal elemental damage, so it can’t resisted that way and it heals the character that uses the spell while dealing damage. If you don’t send him down any other paths, Wakka can get this spell relatively early in the game. This is a great spell for both Lulu and Yuna to learn with a Black Magic Sphere, though Yuna needs it slightly less.
Osmose – This spell is painfully hard to learn. Wakka will learn it eventually, but not in the early part of the game. Auron can learn it by spending two Level 2 Key Spheres or one Level 3 Key Sphere, but that is pretty much a waste for a character that won’t even be with you all the way until the end of the game. The main reason to never deviate with Wakka from his normal route is so he can get to this spell as fast as possible. It is the one spell in the game you can always cast, since it doesn’t cost magic points to cast and it drains magic points from an enemy and gives it to the caster. That is useful for every character in the game. In fact, once Wakka learns this, every other character should use Black Magic Spheres or Teleport Spheres and Return Spheres in order to immediately learn this spell, starting with Lulu and Yuna.
Ultima – If this weren’t the hardest spell in the game to learn, it would be the best. It is like Flare, except it hits all enemies. Unfortunately, you either need a Warp Sphere or a four Level 4 Key Spheres to learn it. If you have that many Level 4 Key Spheres, you can learn much better spells and skills, like Auto-Life, Full Life, Copycat, or Doublecast. Unless you have more Key Spheres than you need, you should only use a Warp Sphere to learn this spell, though make sure you have a Return Sphere to leave afterwards.