While it is true that Bel and Czern were a pair of partnered Grisha, this is because they were Grisha first. The Grisha practice of partnering is not because of Bel and Czern but for the same reasons.
Too much emphasis is put on the ‘small science’, as though there could ever be a meaningful division between that which most Grisha do and merzost. For otkazat’sya, it is an useful illusion, a distinction to help them find a reason to tolerate the existence of Grisha without thinking too hard about ‘witchcraft’; for Grisha, it is a warning. Grisha must always balance control and release, power and safety. Grisha must be small gods, lest they be seen more as witches than people and die for it.
Partners serve both purposes. Like mountaineers or climbers lashed to one another for safety as they scale a mountain, Grisha naturally gravitate to one another for both safety and strength, and in the act of striving often form lifelong bonds. Twins are almost always both Grisha, if either one is, as they are of course of the same stuff; and close sibling pairs often form the most natural partnerships. But most Grisha come to their studies singly and meet a partner at the Little Palace. Like calls to like and most often Grisha partner within an order. This seems obvious for the Corporalki — how much more powerful a Heartrender who can feel another’s heartbeat as though it is inside their own chest? how much more skilled a Healer who knows another’s body as close as their own? — but the value goes beyond those who focus on life and death. How much easier to pull the wind when two people have learned how it flows through them? How much more elegantly crafted when four hands know the metal than just two? A tide requires both a planet and a satellite. Sometimes it is the complement that is needed: Bel and Czern, light and shadow. While it is generally better to have a like partner than that of another order, better to be two Heartrenders together than a Durast and a Tailor, sometimes the complement in personalities makes up for a mismatch in talents. Far better to have a strange match than none at all. Twinned is best, but better triplets than a singleton: better two hands that shake than only a single steady one.
The push-pull of striving for more power but pulling each other back from some invisible brink allows both to achieve greater things more safely than if they were alone; and especially in the absence of orders and palaces and formal instruction, it is the way Grisha have always tended, have always learned by teaching each other, have always nurtured and fed each other with their magic. And here I say something that few who are not Grisha properly know, and fewer still truly understand: becoming Grisha means unbecoming people. It has been said in many ways, that ‘good, normal people don’t do what Grisha do.’ This is true. Good, normal people from Fjerda to Shu Han know their roles and stay in them; they live in their huts and have their children; enjoy a kvas or a dance but never too much; pray for good weather and good hunting and good harvests without imagining they might control any of them; work in a factory or a field and produce things only as fast as they naturally come. Grisha have a little palace, true, but own no huts nor anything else. Grisha women and men hold little respect for the differences of sex. Grisha are as likely to make partners of their own sex as the opposite, and the walls of the Little Palace know what happens by the dozens after holidays and fetes. Grisha might have children, but they’re either as strange as them or strangers to them. Grisha’s needs are immoderate: either too much magic or too much kvas (or worse, jurda parem). Grisha must exercise their magic or get their exercise elsewhere, fighting, gambling, tumbling, dancing, reckless acts that disrupt the peace and disturb the people. The kefta they wear are not just protection, not just a badge of pride, but a warning. Grisha know the difference between a purple and a blue kefta, the story that the embroidery tells, but people see only a Grisha. Beware, people.
Perhaps you are asking, why must it be this way? Perhaps a Grisha can be a half-measure of a person: put the Healers in the hospital and the Durasts in the factory, let them out of their palace and give them their huts, and let the priests teach them the values of temperance and the austerity of the saints. True, things could be improved. But even were the powers that be content to let the Grisha out of their sight, even were they content to mix a reckless Second Army with the orderly rank and file, some problems would persist as long as good, normal people do. One must always choose — light or dark, Grisha or people — because the way to becoming upstanding folk is a straight back and strong limits, and the way to becoming Grisha is disinhibition. Grisha children can be found through sudden pain. Grisha magic can be unleashed through stress and rage and exhaustion and adrenaline. Can anyone practice being one thing all day and the opposite all night? Be a whore each weekday and a nun at the weekend? A drunk in the tavern but a teetotaler at home? But here is the cosmic joke: Grisha can’t be people even if they tried. There is no way to put away the magic, to cage it either deliberately or ignorantly, without it trying to get out, without it wearing away at that straight back and those strong limits, like water eroding rock. No way to avoid it, few ways to hide.
This also forms part i of The Shape of Things to Come.