Lights

Gaseous Investiture within the Rosharan system manifests as a number of different Lights, each associated with one or more Shards. These Rosharan Lights include the three pure ones -- Stormlight, Voidlight, and Lifelight -- a few hybrids (Warlight and Towerlight being the only confirmed ones), and the anti-Lights.
== Characteristics & Attributes ==
Although the Lights of Roshar come from different Shards, they all share a few fundamental attributes, properties, and behaviors. 
=== Physical Properties ===
All Lights share some characteristics with regular light (i.e. electromagnetic radiation) and matter -- specifically gases and liquids -- though they are neither one of these.
The comparison between light and Light is, in some ways, the easiest to make -- regular light cannot be captured in gems, and it appears to be emitted by any one of the Lights (specifically, the Lights allow the Spiritual Realm to "shine through"). There are some subtle differences, however. When refracted through a prism, regular light forms a rainbow, with all colors getting an even share in the band, smoothly transitioning from one to the next; the illumination given off by the Lights, however, forms a physical impossibility -- a rainbow with specific colors (e.g. blue for Stormlight) getting a larger share of the overall band. Hybrid Lights, such as Towerlight, behave even more strangely -- they split into two rainbows, matching their constituent Lights. For example, Towerlight will split into one rainbow with a wider blue band, and one with a wider green band, matching the rainbows produced by Stormlight and Lifelight.
The similarity with liquids is more subtle, and manifests most clearly when transferring Light between gems using sound vibrations, where it behaves similarly to the way liquids can be siphoned from one container into another (though the actual mechanics behind this are different). Once the transfer begins, the Light will follow the source of the sound, much like how a liquid will flow through a siphoning tube or hose. This parallel holds even when transferring Light directly from one gem to another using the Arnist Method, though the process there is more akin to osmosis.
And finally, the similarities with gases are most evident in how Light behaves when it is not doing anything -- it diffuses through porous surfaces, rises in the air, and "evaporates."
=== Interaction with Gems ===
All Lights can be stored in gems. How long a given quantity of Light will remain in a specific gem depends on the type of Light and the quality of the gem. The rate at which a Light leaks from gemstones is not constant either -- it appears slow at first, but accelerates rapidly near the end, making gems that begin to dim, dim fast. Regardless of the type of Light, perfect gems are said to be able to hold it indefinitely, but they are extremely rare.
Light can also be transferred between gems. Prior to the occupation of Urithiru during the True Desolation, the methods of transferring Light -- only Stormlight at the time -- from one gem to another were closely guarded secrets of the different artifabrian communities.
==== The Arnist Method ====
The Arnist Method of transferring Light between gems is a procedure involving draining the Light from a small(er) infused gemstone and moving it into several large(r) empty ones of the same type; the procedure is reminiscent of the movement of gases across a pressure differential, as Light will naturally and passively leave a smaller gem and flow into a nearby larger one.
==== The Vriztl Guild Method ====
There exists at least one alternative to the Arnist Method, and while it doesn't have a formal name, it is known to the Vriztl Guild of Thaylenah -- and it traditionally involves tuning forks and sound. If a gem can be made to vibrate at a frequency matching one of the pure tones of Roshar, it will draw nearby Light corresponding to that Tone (e.g. a gem vibrating to Honor's tone will draw Stormlight in). To transfer Light from one gem to another, the artifabrian would first use a tuning fork matching the desired tone, and touch it against the full gemstone, making it vibrate with the same frequency. The gem and fork vibrating at a matching frequency allows the artifabrian to lead a line of Light from the full gemstone to an empty one, which -- when touched by the tuning fork and also made to vibrate at the matching frequency -- would proceed to siphon the Light from the originally full gem, though a small amount of Light is lost in the transfer.
=== Intent === 
Light, much like the Shards it comes from, has Intent. The full scope of the importance of this Intent is unclear, but it appears critical for the creation of hybrid Lights and anti-Lights.
== The Tones ==
One of the most unique ways the Lights of Roshar behave unlike regular matter is in the way they naturally vibrate. Each Light vibrates at -- and responds to -- not only a specific frequency (matching the pure tone of its Shard), but also to a specific rhythm. For example, when singers listen to a Stormlight sphere, they can faintly hear Honor's pure tone wavering and pulsing to a stately rhythm -- Honor's rhythm. Hybrid Lights, such as Towerlight and Warlight, complicate this further, as they have two tones (e.g. in the case of Towerlight, Honor's and Cultivation's), somehow different from what they would be in the constituent Lights, changed to be in harmony with one another; both tones adopt a rhythm, once again different from the rhythms of the hybrid's "components" -- for example, both of Towerlight's tones vibrate to the Rhythm of the Tower. The combination of a Shard's tone and rhythm is sometimes referred to as the Shard's song.
The relationship between Lights and their tones goes in the other direction as well. The same way the harmony of a Light's tone and rhythm can be felt and heard, one can create this harmony using musical instruments, or even one's voice, and thus draw the Light in. In fact, Raboniel speculates that the reason Light responds to sound, and the combination of a specific tone and rhythm, is because it is reminiscent of the "voice" of the Light's Shard. The Vriztl Guild of Thaylenah, likely unaware of the Realmatic reasons behind it, has been making use of this property of Light to transfer Stormlight between gems -- in their case, using tuning forks matching Honor's tone.
=== Opposite Tones ===
There exists a set of tones complementary to the pure tones of Roshar, identical in frequency, but created and infused with Intent. These tones, sometimes called "opposite tones" behave similarly to the pure ones, in that they too interact with their matching Light (e.g. Stormlight will interact with Honor's opposite tone), but where the sound produced by the pure tones attract Light, their opposites repel it. Intent plays a critical role in the creation of these opposite tones, as they cannot be created by accident, one must Intend to produce them, though there exists a caveat: an opposite tone can be produced mechanically, with a musical instrument and with no Intent, as long as the instrument was created with the Intent of producing an opposite tone in the first place.
Related to the opposite tones' ability to repel Light is the strange way they sound differently to different people. For example, Odium's tone and its opposite sound identical to a human, but to a Fused -- somebody whose soul has been heavily Invested by Odium -- the opposite tone sounds uniquely unpleasant.
Naturally, since the opposite tones sound exactly like their pure counterparts, they can be made to be fit their respective rhythms; the same way Honor's pure tone can harmonize with his rhythm, so can his opposite tone. This Intent-fueled song is crucial for the creation of anti-Lights.
== Pure Lights ==
There are three primary, or "pure" Lights in the Rosharan system, one for each Shard. 
=== Stormlight ===
Honor's Light has been a core part of life on Roshar, both literally in the renewing and refreshing energy it provides to the planet's flora and fauna, and figuratively -- in the numerous ways it is being used by people in their everyday life. It is delivered primarily through the highstorms, and glows with a steady white light, with a slight, nearly imperceptible blue tint. When its illumination is split through a prism, it produces a rainbow with a larger blue band. When drawn in and held by a Surgebinder, it encourages motion and action. Stormlight's -- Honor's -- rhythm is a stately one.
=== Voidlight ===
Historically, Odium's Light only found its way to Roshar during Desolations when Odium -- or in the case of the False Desolation, Ba-Ado-Mishram -- would supply it directly to his servants, provided they sang the Song of Prayer. Since the arrival of the Everstorm, it can be obtained much more easily -- though it appears that it doesn't naturally infuse gems in the way Stormlight does during highstorms. Like Stormlight, it can be stored in gems, but it leaks much more slowly -- possibly the source of Szeth's belief that the Voidbringers can hold Stormlight (in actuality, Voidlight) indefinitely.
Voidlight glows with a distinct purple-on-black glow dubbed "hyperviolet" by the Ardent Rushu to Navani Kholin during their fabrial research in the year 1175. When its illumination is split through a prism, Voidlight produces a rainbow with an "enormous" violet band, dwarfing all other colors. When drawn in and held, Odium's Light enflames emotions, though in singers at least it doesn't infuse their entire body like Stormlight does, instead going to the gemheart. Its rhythm is "chaotic, but with a certain logic to it."
=== Lifelight ===
Lifelight, or Cultivation's Light, is perhaps the rarest of the three pure Lights. Lift is uniquely able to produce it by metabolizing food, but no other ways of obtaining it are currently known. It appears very similar to Stormlight, a nearly pure white light, but where Stormlight has a slight blue tint, Lifelight has a slight green one. When its illumination is split through a prism, it produces a rainbow with a larger green band. Its rhythm is stark and staccato, but it builds. Lifelight shares Stormlight's effect on plants but to a superior degree, stimulating their growth when combined with the proper rhythm.
== Hybrid Lights ==
In addition to the "pure" Lights of Roshar, there exist hybrids created by the union of any two pure Lights. The methods of creation of these hybrids vary slightly, but at their core is the need for the appropriate Investitures, tones, and rhythms.
=== Towerlight ===
Towerlight is the very substance of the spren known as the Sibling, and as they are the child of Honor and Cultivation, so Towerlight is the product of melding these two Shards' Investitures, tones, and rhythms. It can only be created by the Sibling and their Bondsmith, though the imprisonment of Ba-Ado-Mishram rendered them unable to produce more than small amounts -- enough to power only the most essential of Urithiru's fabrials; a deficiency that appears to have ended when Navani Kholin became the Sibling's current Bondsmith. A key factor in the creation of Towerlight is the Sibling's ability to hear both of their parents' songs -- Cultivation's, which they could hear and sing on their own, and Honor's, which Navani had to provide for them. Because of this, it is unclear whether the Sibling is truly "healed", or losing the bond -- and Navani -- would mean that they lose Towerlight once again. 
When the Sibling is fully awake, Towerlight is readily available throughout Urithiru and will power all of its fabrials. It also fuels Surgebindings for longer than Stormlight, keeping them active for hours. When brought outside of Urithiru, Towerlight almost immediately completely leaks away from both gemstones and humans.
In appearance, Towerlight resembles both Stormlight and Lifelight, as it glows with a soft blue-green light. When split through a prism, it produces two rainbows of color, one with a wider blue band, and one with a wider green one. Towerlight's rhythm -- the Rhythm of the Tower -- evokes the "boundless energy of Cultivation, always growing and changing, and the calm solidity of Honor -- organized, structured." Holding Towerlight has a calming effect.
=== Warlight ===
Unlike Towerlight, which has been known to humans and singers alike for millennia (even if knowledge of it was largely lost on Roshar after the Recreance), Warlight -- the hybrid Light of Honor and Odium, who would later form Retribution -- is a recent discovery, one that even renowned singer scholars like Raboniel thought an impossibility. During the occupation of Urithiru, Navani discovers that a human and a singer (or at least she and Raboniel) can create Warlight by allowing Stormlight and Voidlight to combine inside a gem made to vibrate to the Rhythm of War -- a rhythm created by the harmony of Navani singing Honor's song and Raboniel singing Odium's. Raboniel did not know that this rhythm existed prior to her research with Navani, and she notes that its emotional influence will be of particular interest to El. It is seemingly impossible to create Warlight without the participation of both a human and a singer.
Warlight glows with a vibrant black-blue light, and its rhythm is a burst of chaotic notes, bounded by a regular, orderly pulse. When contained in a gemstone, the Light can be seen oscillating between swirling like a raging storm and then falling into a peaceful calm.
=== Odium & Cultivation ===
The existence of an Odium and Cultivation hybrid Light hasn't been confirmed, but Venli successfully attunes a rhythm of these two Shards, so a corresponding Light is likely.
== Anti-Lights ==
Physical matter is known to have a counterpart called antimatter -- matter composed of antiparticles that share many properties with the particles of ordinary matter, but manifest some of them in an opposite way (e.g. a proton and an antiproton have the same mass, but opposite electric charges and magnetic moments). Raboniel describes this in terms of axi with opposite polarities. A similar relationship exists between Investiture and anti-Investiture in the cosmere. Anti-Investiture -- or, in Roshar's specific case, anti-Light -- comes in a number of different varieties, each one of which shares some properties with its corresponding ordinary Light, while exhibiting other attributes in an opposite way. Most notably, a Light and its anti-Light that come in contact will naturally annihilate each other -- Navani and Raboniel theorize that it may be more violent when the two are brought together under pressure, such as within a gemstone. This occurs when any Investiture and anti-Investiture come into contact, though the explosion is smaller if they are not both of the same Shard.
Anti-Light shares most of the physical and magical properties of ordinary Light: it glows in the physical spectrum (though unlike regular Lights, it appears to warp the air around it, almost as if it is drawing light instead of emitting it), it can be stored in gems, it responds to sound and vibration, and has Intent. One area where anti-Light differs from regular Light -- or at least the pure ones -- is that it requires Intent to be created, a property it shares with the hybrid Lights. The only known method of creating anti-Light requires dampening the natural vibration of its corresponding Light, isolating it from its Shard's pure tone, and then re-writing it with a different tone, one that has been inverted with Intent. One way to do this involves putting the ordinary Light in vacuum and allowing it to draw near a gemstone that has been made to vibrate to the tone of the desired anti-Light -- the ordinary Light's opposite tone.
Much like each Light's natural vibration can be heard or felt by different species, anti-Light's can too, though its song is not just physically audible, it carries a magical effect too. For example, to a human the song of anti-Voidlight will sound identical to the song of Voidlight, Odium's tone moving to his rhythm, but to a Fused -- whose soul is filled with Odium's own Investiture -- the song of anti-Voidlight not only sounds different, it also causes intense pain, similar to the discomfort they feel when hearing Odium's opposite tone, but much worse. The type of Investiture an anti-light is keyed to can also have an impact on its reaction to types of Investiture, this can only alter the intensity of the explosion caused however.
=== Anti-Voidlight ===
Anti-Voidlight is the first anti-Light to be discovered on Roshar, initially discovered by King Gavilar Kholin not long before his death. His research into the Lights of Roshar and the ability to transport them between planets in the system allowed him to obtain a sphere of anti-Voidlight, which he gave to Szeth moments before dying. The sphere, and the anti-Voidlight within it, eventually led Navani to also discover how to create anti-Light.
Anti-Voidlight glows faintly violet-black and appears to faintly warp the air around itself. Its tone -- and song -- sound identical to those of Voidlight, but they induce an adverse reaction in the Fused, and presumably in other creatures heavily Invested by Odium, such as Voidspren. When made to touch the soul of such creatures, anti-Voidlight reacts violently against the Voidlight there, resulting in permanent death.
=== Anti-Stormlight ===
Anti-Stormlight was discovered by Raboniel shortly after Navani's own discovery of anti-Voidlight. In many ways, anti-Stormlight behaves symmetrically to anti-Voidlight -- except where anti-Voidlight has a destructive effect on beings Invested by Odium, anti-Stormlight has that effect on ones Invested by Honor, such as Radiant spren. Using Raysium weapons, anti-Stormlight is able to kill Radiant spren, which breaks the bond between the spren and its Radiant.
A Dawnshard would be more dangerous to Anti-Stormlight than the other way around. It is likely, but unconfirmed, that this is the case for all Anti-Investiture.
=== Other anti-Investiture ===
It is unknown whether hybrid Lights or Shards outside of the Rosharan system have anti-Investitures of their own. Khriss states that, though long theorized, the anti-Lights are her first evidence of an anti-Investiture.
== Notes ==
es:Luces