Light is the Kethic element of radiance: the brightness of a thing, the glare thrown off open water, the beam that splits a dark room and the dazzle that blinds the eye looking into it. A shaper channels emotion through Kunus, the light layer of the Elemental Planes, and bends light to intent, kindling a cold glow with no flame under it, narrowing a shaft fine enough to read by at midnight, or loosing a flash that leaves a swordsman blinking at spots.
The feeling that feeds light is the feeling that wants to be seen. Clarity, conviction, the hard certainty of being in the right, a joy that announces itself: these are the registers Kunus answers to, and it answers grief or secrecy badly or not at all. Light only ever adds. It lays brightness over what was dim. A dark-shaper seems to do the reverse but works the same way, calling up shadow as a substance with a weight of its own and setting that presence into a space. Only a void-shaper takes anything away, drawing presence back out of a space and leaving nothing where it stood.
The openness cuts both ways. A shaper who throws a glare across a courtyard is lit in the middle of it, plain to everyone there, and a working forced past its limit stops revealing and starts to blind, the caster's own eyes among the first to go. The dark-shaper's danger is that he cannot see. The light-shaper's is that he cannot help being seen. At the scale of a whole seam the same over-expression does not just blind, it scours: the Temple of Bryn in the Sandreach was burned to glass when the Kunus seam under it surged past what the ground could hold, and that stripped, untended seam still forces any light-working near it past the size its caster aims for.
Light sits awkwardly with the people most drawn to it. Bryn, the spotlight-sun, is sentient and widely worshipped, and the sun-temples that sing his path across the sky take to light-Kethic readily and assume the two are one and the same gift. They are not. The radiance a shaper works comes through the Kunus seam, the same borrowed conduit as every Kethic element, and Bryn grants a light-shaper nothing he would not grant a stranger. Most sun-priests dislike hearing it, and in the stricter congregations a shaper who says so out loud finds the temple doors closed to him.
Light is credited with more healing than it earns. It does not knit a wound or set a bone, because that is not what light is. What it does is narrower and real. A focused beam burns the rot out of a wound that would otherwise turn. A steady glow held over a sickbed eases the failing and gives the dying something gentler than the dark. A blind-flash can end a fight before it costs anyone a life. The reputation for mending flesh is folk hope dressed up as fact, and a light-shaper at a deathbed brings comfort, not a cure.
Kunus seams are rare, tied to high and exposed places where the light layer presses close to the world, so most who work light train nowhere near one and keep to small, certain effects. Mastery runs along the same three axes as any Kethic discipline, set out under Kethic: interior control drilled until the feeling comes exactly as needed and no more, a channel deepened by long use, and a teacher who can sharpen the craft but can never hand over the attunement itself.