As others have said, blindness exists (along with an absolute slew of other injuries, maladies, diseases, and incurable afflictions) with two of the most notable examples of blind characters being Shamani Lohmani and Y'shtola, along with many an eyepatched individual like Rostnsthal.
Trauma (magical or physical) seems to be the most common cause, though there's also a disease called Ceruleum Eye which causes temporary blindness. It's possible also to go blind or be born blind I'm sure. As far as treatments go, there seems to be no reversing permanent blindness. Shamani Lohmani and Y'shtola are permanently blind, though the latter has found a magical way around this. Eye Drops are able to reverse and treat temporary blindness, however. That said, we've seen no evidence of braille or seeing-eye animals. There's probably not braille, but having a guide dog or other tamed animal does not seem implausible. Go for it!
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Arcanist, Scholar, and Summoner tomes are all drawn with aetherially conductive inks and that ink is drawn in specific geometries or patterns that produce a spell. The geometry is the focus, the ink is an accelerator for your own aether. As far as tomes go - the contents of each differs based on the person who penned it. While most of the grimoires in game all show the same few pages, in lore, you're likely looking at a different geometry (and therefor a different spell) on each page. So a book could contain maybe hundreds of spells, or, as far as Nymian Scholar tomes are concerned, many pages worth of military strategems and tactics interspersed with various relevant spells.
Encyclopedia Eorzea: “A form of arcane art using esoteric calculations, arcanima was developed originally by the people of the south sea isles. After discovering a means of expressing natural phenomena in mathematical terms, they refined formulae into arcane geometries - precise patterns that allowed practitioners to weave aether into specific magical effect. This, in turn, bore the school of arcanima.”Anonymous Arcanist: “For an arcanist to weave his spells, he must conjure in his mind the image of distinct mystical diagrams known as arcane geometries. These geometries are inscribed upon the pages of a grimoire, such as the one you constructed at my request. The most important aspect of any grimoire is the quality of the ink used to illustrate its pages. Geometries drawn with ink that is especially conductive to the flow of aether allow the arcanist to more effectively channel his magical strength.”________________________________________________________________Camate: “Many grimoires can be wielded by arcanists, scholars, or summoners. However, each grimoire is tailored to a single profession, which can be determined by examining its contents. Arcanist grimoires contain geometric symbols that shape and direct the power of arcanima; summoner grimoires contain incantations used to call forth and command primal egi; scholar grimoires contain a wealth of tactics and stratagems which can be applied during battle.”
Yes, according to Alka Zolka you need a soul crystal to be a Nymian Scholar. That's where the Scholars of Nym bound their fae familiars to. Soul crystals in general act as aether and memory storage, aiding later generations who resonate with said crystal with memories of techniques long lost. This seems to also be true of the Faery bound within the soul crystal. Their memories and personality are stored there. In the case of the SCH storyline, Lily, our fae, had lost her memories because she had been dormant for so long and her memories seemed to unlock as we grew as a Scholar and unlocked more of the soul crystal. As for where we keep our soul crystals, the lore book tells us that they are worn close to the skin.
Alka Zolka: “According to the tablet, the crystal from which the faerie sprang forth is called the Soul of the Scholar, and it contains the wisdom of those long-dead Nymian mages. With it, you can call upon the faerie as you did before and bind her to your will.”Las Vegas Lore Panel - Q: “To follow up on a question from the stream earlier- the taxonomy that fairies fall into. Is there an origin to how they become fairies of Scholars. Were they fairies and then bound to scholars? or did the scholars create them?”
MCKF: “Yes, the second one. Fairies again, while they fall under the taxonomy of elementals, they are actually beings that were created. They did not exist before. The Scholar would take the energies and elements from around them and would basically create these beings that were made of the elements.”
Q: “Those are bound to the soul crystal then and passed from one person to the next where carbuncle is more one per person. Very cool.”Surito Carito: "I do not know how that soul crystal came into your possession, but I am glad that it did. For the sickness robbed me not only of my body, but of Lily as well. The Soul of the Scholar no longer resonates with my aether. I cannot summon her─only you can. Only you are fit to wield the magicks now."Alka Zolka: "The treatise indicates that Nymian scholars wielded a far more diverse repertoire of spells than you currently possess. Precisely why you lack these spells, I cannot say. However, the fault may lie with your faerie. One could surmise that the knowledge contained within the Soul of the Scholar is essentially hers. Therefore, if she cannot remember the ancient magicks, it would suggest that... Hm. A thought occurs to me. If it is indeed the case that the faerie, having been sealed for fifteen hundred years, has yet to fully regain her senses, mayhap visiting a familiar location would hasten the process."________________________________________________________________Encyclopedia Eorzea: “Ever since the height of the Allagan Empire in the Third Astral Era, the practice of using crystals to store and impart knowledge has been prevalent in Eorzea. An adornment known as a “soul crystal” is worn close to the skin, where the uncommonly clear facets of the carefully cut shard catch and transcribe the ebb and flow of a soul’s aetherial composition - effectively capturing an imperfect echo of the wearer’s memories. This arcane tool engraved with the myriad deeds of heroes from eras past was employed by many of the disciplines of yesteryear to preserve and pass on the skills of successive generations of masters.
The wisdom contained in a soul crystal, however, is not so easily drawn forth - an untrained neophyte cannot simply pick up one of these gems and expect his mind to be flooded with the knowledge of advanced spellcraft and combat techniques. Without first attaining sufficient proficiency and tempering one’s soul to mirror the maturity of the crystal’s contributors, a prospective student will be denied even the slightest glimpse of enlightenment. Thus, as is the case with the more contemporary disciplines, the key to mastering the secrets of a soul crystal lies in diligent study and training.”
They do have their own sentience and personalities, and they can disobey their Scholars. We even see evidence of this in the 30-50 SCH questline, wherein Lily regains enough of her memories to protect a tonberry from Alka Zolka.
Alka Zolka: "Though... does she possess memories, like you and I? Until recently, I had no idea faeries even existed. It may be ages before I gain an understanding of these otherworldly entities...
Then this strongly suggests that each faerie is a distinct individual with her own thoughts, feelings, and memories..."Alka Zolka: "What are you doing!? Move, damn you! Confound it all! Bah! What happened, Forename!? I thought you could control her! <sigh> I apologize. I know you have only just begun to work with the faerie. Some...disobedience is to be expected.Alka Zolka: "<sniffle> <sob> I...I nearly killed him! Thank the gods that faerie stopped me. I wonder...did she know it was Surito from the beginning, or was it only... In any case, she has regained a good portion of her memories, if not all of them, I suspect."
Hope this helps!