When Magic Booster is used in the 2013 PC re-release, the player's inventory gains 100 Blind spells, among other basic spells.
Blind can be drawn from many enemies at all levels, and can be refined from Ochu Tentacles using the Guardian Force Diablos' ability ST Mag-RF. This makes Ochus a good source of Blind, for both the Ochu Tentacles and to draw the spell. Ochu's cards also modify into its tentacles.
Blind when cast will inflict the Darkness status effect on a target that is not immune to it. This reduces a target's Hit Rate by 75%, causing most of their attacks to miss. Squall and Seifer have native 255% hit rate, but can't deal critical hits when blinded.
Blind can be cast using the Magic command, Selphie's Slot Limit Break, or Rinoa's Angel Wing if she has it in her inventory. Casting Blind in battle increases compatibility with Doomtrain by 1 and with Siren by 0.6, but lowers compatibility with Cerberus and Carbuncle by 0.2. It can also be junctioned to inflict or resist against the Darkness status.
Blind can be junctioned to ST-Atk-J to inflict Darkness on enemies with a physical attack, allowing a character permanently inflict Darkness against enemies that are vulnerable to it. This can be useful against enemies that primarily deal physical damage, causing most of their attacks to miss, making it a strong choice early on to junction to ST-Atk-J. However, junctioning Sleep to ST-Atk-J can in a lot of cases have a similar desired effect, meaning it is best to do this only in instances where an enemy is immune to Sleep but not to Darkness.
Blind can also be junctioned to ST-Def-J to resist against Darkness, and 100 Blinds immunizes against it. This is often crucial for party members that deal physical damage (though it is mostly unnecessary for Squall as his base hit rate of 255%).
In both cases, Blind is outclassed by Pain. This is because Pain can not only inflict or provide full resistance to Darkness, but also has the same effect for Silence and Poison (and additionally gives resistance to Curse). As a result, Pain can provide full immunity to four statuses with on ST-Def-J slot, or inflict three statuses with the ST-Atk-J slot, making Blind redundant. In this case, Blind is only useful when the player wants to inflict or resist against Darkness, but is using Pain to junction to stat boosts (as Pain is useful in this regard), but otherwise the player may prefer to simply remove Blind in favor of an additional magic slot.
Drawing Blinds from the Dollet Communications Tower draw point and then using it against Diablos is especially useful, as Diablos can only kill the party with his physical attacks, his other attacks dealing fractional damage. This way, the player can defeat Diablos quite easily even right after he first becomes available to fight.