Magic is a science that requires constant study and experimentation. Old magic is often outdated and doesn’t work anymore. That’s because the science of magic is much like computer science… the medium you’re playing with changes with time. Some fundamentals will always be true, but when it comes to casting spells you’re dealing with a different set of rules than you were 5 years ago.
In magic, the universe can be considered a single machine of many parts governed by rules. There are several fundamental logic gates that all information must pass through for anything to occur. A few of these gates are conjuration, transmutation, and evocation. These logics are constantly parsing the state of all things in the universe in order to determine what needs to happen next. When an alchemical reaction occurs, it’s because the transmutation logic determined that X+Y=Z.
There are many means by which information can be passed to these logics and they are known collectively as ports. Some of these ports are harder to find than others, and the more a port is used the better it gets at learning what information is legitimate and what’s erroneous or malicious. The mechanism by which they do this is under academic dispute, and we’ll get to it in a minute. Ports die and are born. A newborn port is highly valuable because it doesn’t yet have great security against illegitimate information. Ports are vital to reality but they are also its greatest flaw; the innate chaos of the inner world (the very small) produces these ports at random, they are holes in the foam of chaos and they are the gates by which the laws of the universe communicate with the world.
Spells are the result of passing illegitimate information to these ports. When a caster of any variety wants to cast a spell, ultimately they are lying to a port, giving it information which when passed to one of the universal logics will result in a desired effect. Depending on the caster, this may be done subconsciously, or via some other entity, or via direct conscious injection. Each logic “speaks” a different language, or more accurately abides by a wildly different set of rules, all of which are highly unintuitive. This, combined with the learning mechanism by which ports improve their safeguards, results in spellcasting being a constant struggle of keeping up to date on the latest research.
The mechanism by which ports learn and improve is a hotly debated topic, ranging from theories on an overdeity outside of the known reality, to spirits which are born in the ports and manually do the work of parsing things that go through. A near-inevitable thesis from a thaumaturgic grad student is some insane but possible new idea on what could be doing it. The general consensus among older and wiser heads though, is that of The Spheres. These Spheres are things like Good, Chaos, War, Death, etc. They are absolutes, they have motivations, and they flex their influence on the universe, trying to dominate the parsing of ports to favor their goals. Gods are islands of sentient Sphere-influence but like all sentient things, they are products of the system, and therefore slaves to it.