Natural Gifts, Training, and Cross-disciplinary Magic

Roughly 1 in 20 people are born with the latent capacity to harness the power of magic, commonly referred to as the Gift. In some, the Gift is weak, while in others, quite strong. Strong Gifts tend to manifest observably, and provide clues to how a person may be aligned to one or more areas of magic, called Domains.
Historically, Domains seem to have been "unlocked" only after a key figure is born with a strong Gift in that area. Once a figure like this is born (usually within their lifetime), new talents crop up showing similar skills. They in turn become followers of the guru, seek training, and over time, develop a collective Tradition. To date, there have been just four personas synonymous with entirely new brands of magic: Beryth, Nurhasi, Keldaroth, and Khajuro. Each is considered the founder of one of the world's four major Traditions.
There are more Domains than there are Traditions, but Traditions group the most prominent Domains together by type. Respective to the major personas listed above: the Berythians deal principally with the Elements of Fire, Earth, Water, and Air; Nurhetics with Dream, Illusion, and Mind; Aurimbics with Fate, Omen, and Metamagic; and The Exiled Tradition with the forces Life, Death, and Time. Outside of the major Traditions exist Domains of some curiosity, but which for one reason or another have failed to prove very useful to mages. If and when they proffered something of broad value, one or more major schools would absorb the knowledge of such magic, and in all likelihood, also the minor tradition that spawned it. This pattern explains why there are so few competing arcane paths outside the big Four.
All trained mages have the ability to detect the Gift in others, developed or not; it cannot be veiled. The exact nature of a Gift's alignment can be harder to unravel, but Masters who've acquired enough experience training apprentices can usually determine a basic leaning at least. Mismatches do happen: the sorceress Nurhasi provides the most famous case, as her native Domain of Dream went unrecognized by the Berythians that trained her - if for the seemingly good reason that it was the first time such magic had ever appeared within the world. While it is rare for a mismatch to owe to such epic causes as her own, it is always more challenging for a student to learn when they are not well attuned to the Domain of instruction. Nurhasi described her own magical upbringing as akin to being forced to write with one's off-hand. For this reason (and of course, due to their colossal waste of time and resources in teaching them) Masters make every effort to ensure that apprentices are calibrated to the magical Domains they specialize in, even if doing so is more art than science.
A student misaligned with a Domain she trains in can approach the ability of an aligned peer, but always suffers some form of disadvantage, however slight. The stronger her Gift (as determined by Magic Score), the greater the disadvantage. She learns new spells and Spell Techniques more slowly, and the spells she can cast may be hindered. However, she shows promise in her aligned Domain, understands the concepts of its discipline with fair ease, and may even demonstrate natural resistances against spells in this group.
Some historical texts suggest that the Gift was used more flexibly in the past. Streamlining magical energies through longer and more structured spellcasting as was done in later years surely enhanced it in power, but at the cost of potential spontaneity. Accounts say that centuries ago, sorcerors mixed and matched Domains as they saw fit, able to share knowledge with each other more readily than nowadays. Beryth, for instance, is described as the Master of all Four Elements, and though none were so successful as he in this regard, his Disciples were skillfully able to integrate at least two and sometimes three of the four within their magical workings.
These days, convention rather than law keeps mages from playing around with spell Domains. Most mages rely on their Order not only for protection and guidance, but for identity, derived in the main from the brand of magic its Order practices. Affiliation is a tribal distinction. Collegiality between Traditions can certainly exist, but at the end of the day, a Berythian is a Berythian, a Nurhetic a Nurhetic, and so on, and cobbling together magic from different sources threatens a Tradition's position in the world by proposing new, hybridized competitors. Another reason stems from theory: the more complex a spell becomes, the less compatible it is with strongly differing Domains. So, while lower level magic can sometimes fold differing Domains together cohesively, these Domains "pull apart" as the spell ascends in strength, a process known as Domain Repulsion. There are a handful of spells around the world which handle Domain Repulsion in interesting ways, and these rare examples form a template through which this wider phenomenon may be understood.