Aeterna PublicaeBoard

It's the sort of universe where you either do or don't have the capacity to use magic. The trait that determines this is basically whether or not you have what are called "magic circuits". You can basically think of them as a second nervous system that flows through the body. How powerful and how much you can use magic is determined by two factors: the number of magic circuits you have, and the quality of the circuits.

There's another part I mentioned a little before. Mage families pass down what's called a "magic crest" embedded in their circuits. It contains spells and other information that they've researched over their lifetime, and when it's time for a successor to take over, it's passed down to the next generation. If the circuits are a "nervous system", you can think of this as an "organ" that's transplanted. Because each heir adds to it over its lifetime, this means mage families that have lived very long have a strong advantage over newer ones.

The type of magic you can use is determined by a few factors. There's several different forms of magic that exist in the universe, but the only one that has any substantial detail on it is the Western type, Kabbalah. You also have your affinity for the elements. This is actually somewhat more complicated than normal elemental systems, and the elements are rather vague and open ended. For example, the main character of the prequel series to Fate/stay night, Emiya Kiritsugu, has the affinities of "earth" and "air". However, he is a fairly weak mage and only has one real ability. Based on the elements listed, you will be surprised to hear that he basically turns the inside of his body into a pocket dimension called a "reality marble" where its structure is identical, but time moves at a different rate. This allows him to essentially move at extremely fast speeds by how others perceive him, but actually it's just that he's moving faster through time.

A bit of a tangent but reality marbles are one of the few ways you can cheat the magic rules. It's an extremely rare form of magic that allows the caster to project his "inner world" over the "world" itself. Because of this, it doesn't last long as Gaia will destroy it fairly soon after in order to correct the error. However, while active, they obey their own rules and logic rather than what you would normally expect. They're essentially the closest magecraft to true magic.

On Alaya, I mentioned Notes at the beginning, but there's another short story called Tsuki no Sango set similarly far in the future. It's the opposite of Notes, as "Alaya" dies in its timeline as opposed to Gaia. So humanity still exists, but they have lost their will to live or continue, and so are slowly spiraling into extinction as fewer children are born every passing generation.

I also am just gonna briefly mention the vampires, because I think the way they handled vampires in the setting is the coolest I've ever seen.

Vampires basically originate from this entity, coincidentally one of the aforementioned Ultimate Ones, by the name of "Crimson Moon Brunestud". He came into contact with Gaia in the far, far distant past and struck a deal. Gaia would make for itself elementals called True Ancestors, based on the form of Crimson Moon. These are basically near-perfect beings. They are immortal, almost unkillable, and they have immense power. They only possess one flaw: an immense desire to drink blood.

There's no reason for it, they won't die if they don't. But it's an extremely strong urge, and once they give into it, they can't stop. They become murderous, blood drinking demons that must be destroyed by their compatriots. When a True Ancestor drinks the blood of a human, their soul itself becomes tainted and corrupted, giving birth to the more common form of vampire, the Dead Apostles.

Dead Apostles have a lot more weaknesses. Their bodies will fall apart if they don't drink blood, they burn away in the sun, and while they are immune to most normal forms of damage, magical weapons or holy scriptures can destroy them. They can, however, create zombie-like familiars that serve them and acquire blood for them, and still are relatively immortal. The highest among them are the 27 Dead Apostle Ancestors, who are all individually really just freaky. They all basically tried to get higher forms of immortality that not-quite-entirely worked.

They're kept in check by the Holy Church, which is basically the hidden arm of the Catholic Church. They have agents all over the world, and they work to exterminate vampires, demons, all sorts of evil nasties of the night, and so forth. They also tend to eliminate mages who use their powers for evil gains. They have a really strained, cold-war like relationship with what's called the Mages' Association, which is kind of what it sounds like. They aren't quite a "guild" or anything that pleasant, more just a vaguely collaborative organization that works to stop the secrets of magic getting exposed to the public. Their rule is basically "Anything is fine as long as you don't get caught". This isn't just a PR thing either, magecraft operates on a mechanic called "mystery" that is rather complicated but essentially means, the less people know about something, the older it is, and the more history it accrues, the more powerful it becomes. Plus self-preservation helps. Mages also tend to keep to themselves for the most part, they guard their secrets and research jealously.

There are some other weird groups out there like the Demon Hunter Clans, and so forth, but those are kind of the main enforcers of why all the supernatural business remains behind closed doors.