Quasilemental Plane of Radiance
Color has power. Color is emotion, passion, a fire in the heart of life. Color is beauty and enrapturement. Color can be the subtlety of a few flecks of paint, or the power of a roiling wall of energy. There is great power in color, a fact that many have some awareness of, but few truly understand. Here, though, in the Quasielemental Plane of Radiance, held between the planes of Fire and Positive Energy, all must acknowledge its majesty.
The Plane of Radiance is a plane full of light, of all conceivable hues and shades; not merely those which the majority of mortals can perceive, but the full and entire range of potential held within itself. As a result, though it is a plane of intense beauty, it is also a plane of intense hazard. Without some form of protection, paper burns, water boils, and wood smolders in seconds upon being brought into this realm. Even those that can survive the heat still find it sweltering nearly as much as the plane of Fire itself. As is commonly said on the plane, "that which can burn deserves to burn". Anyone in the plane of Radiance takes damage as extreme heat; any level of fire resistance prevents this effect. Further, even if one has protected themselves from the temperature, the light itself is still so piercing that a person is sure to be permanently blinded in moments even through closed lids, though those that have suffered this say that their last sights on the plane were of a beauty that could never be matched anyway. Here, even a spell of darkness can do little more than provide shade. Treat the plane of Radiance as though it was of a light level one step above bright light. Any on the plane with some form of sight must make a Fortitude save each round at DC 30 or be blinded unless the light level is brought below this point; no spell or effect, however, can reduce the light level below normal light. And of course, being of no proximity to the plane of Air, any guests must likely bring their own or soon suffocate.
With no solid surfaces to speak of but for the occasional elemental pocket, movement here must proceed as with many of the Inner Planes, through either some manner of flight or through subjective gravity. Some non-natives provide transit around the plane via ships that travel the colors much as riverboats, great mirrored wheels churning through the hues. Others occasionally use wings of the finest, most well-polished copper, bronze, or at times even silver to propel themselves about with more grace and ease than managing one's gravity by force of will. Any such mirrored surface can provide some level of propulsion, pushing against the onslaught of light, but the wider the mirror or the more perfect its reflection, the more effective it will be at imparting momentum.
Of course, when discussing such a means of propulsion, mention must also be made of the so-called "color storms" of Radiance; times when the natural churn of the hues of the plane grows even stronger, the light taking on more substance than usual as the energies clash against one another. Though these storms are of little more direct danger than usual to a person's life, they are a great danger to those that travel in this manner, much as trying to fly or sail through a hurricane. Those caught in such an event can at times find themselves thrown days, even weeks of travel from their destination, hurtling through the plane with much force as they are bombarded with strange hues.
Despite the troubles Radiance poses to them, there are still mortals that seek it out for a wide variety of reasons. The only significant outpost is the Kingdom of the Blind (truly, more a city than a kingdom) within a massive mineral pocket in Brighthome, near the Glowing Dunes; here, any and all guests are welcome to relax and ease their weary eyes. There are, however, smaller spots here and there where mortals have made their homes — artistic retreats, largely, along with the assorted "colonies of enlightenment", where philosophers from across the multiverse come to seek wisdom and learning from the minds of the local quasielementals, and a number of smaller monasteries where the Initiates of the Sevenfold Veil come to pay homage to that which they see as the source of all magic.
Vortices within the plane of Radiance are rarely welcome passages, as most commonly they open to the depths of stars upon the Prime, though occasionally they make temporary connections with especially powerful infernos or other transient eruptions of pure light or heat. Most other portals are similarly transient on the Radiance end, shifting location with the currents of tint. They most often open to the Upper Planes (leading to a number of lantern archons taking the occasional "vacation" to the plane when they wish to relax), though a significant one is known near Manticore's Breach upon the Outlands.
Ablaze with heat and light as it is, it's likely no surprise that upon the plane of Radiance, spells of fire are enhanced while those of water are diminished; spells of light and darkness respectively are similarly effected, again to no great surprise. Many spells that draw upon the force of light further find themselves with an additional twist as they draw upon the colors of the plane. Spells with the "fire" or "light" descriptors are heightened by 1 spell level, and all spells of the "fire", "light", or "electricity" descriptors are cast as though effected by Flaring Spell. Spells with the "water" or "darkness" descriptors are impeded. And of course, those spells that more directly draw upon the power of color are even more greatly enhanced. Spells of the "pattern" subschool of illusion, or spells with "prismatic" in the name, are maximized.