Runes are special items in The Legend of Zelda: Breath of the Wild. They are spells added to the Sheikah Slate and Link can cast them from it. Each of the four Remote Bomb, Magnesis, Cryonis and Stasis Runes are obtained from a Guidance Stone at the start of each of the four Shrines found across the Great Plateau. After completing the quest "Locked Mementos" and obtaining the Camera Rune from the Hateno Ancient Tech Lab, Link can visit Purah to upgrade some of his runes to boost their effects.
The rune concept resembles mobile apps as they allow Link to use the Sheikah Slate in different ways and are basically applications that can added to the Sheikah Slate which is similar to a real world mobile device.
List of Runes
| "Detonate the explosive using a remote trigger."|
"The force of the blast can be used to damage monsters or destroy objects. There are both round and cube bombs, so use what would be the best fit for the situation."
|Ja Baij Shrine|
| "Manipulate metallic objects using magnetism."|
"Grab on to metallic objects using the magnetic energy that pours forth from the Magnesis Rune. Objects held in the magnetic snare can be lifted up and moved freely."
|Oman Au Shrine|
| "Stop the flow of time for an object."|
"Objects stopped in time will store kinetic energy. This stored energy will be expelled when the flow of time resumes. Making good use of the stored energy can move even the largest of objects. Take note of the time needed to recharge it."
|Owa Daim Shrine|
| "Create a pillar of ice from a water surface."|
"Builds ice pillars that are very stable. These pillars can be used as stepping stones or as obstacles. Use Cryonis on an ice pillar to break it."
|Keh Namut Shrine|
| "Instantly render a visible image into a picture."|
"Pictures created are saved in the album. It has a useful feature that connects to the Hyrule Compendium and automatically registers pictures of new entries."
|"Locked Mementos" reward at Hateno Ancient Tech Lab|
| "Use an amiibo to summon something useful."|
"You never know what's going to come through whe you use it. Some amiibo can only be used once a day."
|Great Plateau, enabled after obtaining one of the first four runes|
Master Cycle Zero
| "Summon Master Cycle Zero"|
"Insert materials into the tank to convert them into fuel. You can freely call upon this item, but summoning it will not work in certain areas."
|Reward for completing "EX Champions' Ballad"|
In addition to these runes, the Sheikah Slate has several basic runes that act as basic functions of the Sheikah Slate, though are not actually listed or appear in the Sheikah Slate's rune section.
The Sheikah Sensor is one of the Sheikah Slate's basic runes according to the Sheikah Sensor Notes by Symin. It is designed to detect Shrines with Hero trials that have not been activated. Link unlocks this rune when he activates the Dueling Peaks Tower in West Necluda. After reaching the Hateno Ancient Tech Lab and having Purah restore his Sheikah Slates missing and corrupted components, Purah offers to upgrade it to the Sheikah Sensor+ in exchange for three Ancient Screws which is revealed in her diary to have been developed by Purah after the Great Calamity during the Age of Burning Fields. Purah started development on it when she was 30 years old and took half a century of research and development to complete, though Purah was unable to add it to the Sheikah Slate as it had been sealed away with Link in the Shrine of Resurrection.
Symin is interested in this upgrade due to the Sheikah Sensor being the focus of his research and gives Link the Side Quest "Sunshroom Sensing" to test it out by taking a picture of a Sunshroom growing behind the tech lab then use the Sensor to find three Sunshroom in nearby Retsam Forest. Symin rewards Link with three Hearty Truffles while the quest acts as a tutorial for the Sheikah Sensor+. Symin also adds information on it in the Sheikah Sensor Notes after the upgrade is obtained.
The Hyrule Compendium is one of the original default runes that existed on the Sheikah Slate when it was owned by Princess Zelda one hundred years prior to the events of Breath of the Wild. However when Link obtains thee Sheikah Slate, the Hyrule Compendium is missing presumably due to the Album's data being corrupted and the Camera Rune being missing, forcing Link to seek out Purah during "Locked Mementos" quest to restore it, the album, and Camera Rune.
By taking pictures of materials, equipment, items, enemies, and creatures Link can unlock an entry for it in the Hyrule Compendium which provides Link with information from descriptions to common locations where they can be found. The Sheikah Slate+ upgrade links the Hyrule Compendium with the Sheikah Sensor, allowing Link to use it to detect things recorded in the Hyrule Compendium.
After completing "Sunshroom Sensing", Symin reveals Purah's Guidance Stone has picture data for the Hyrule Compendium that can fill in missing entries and Purah allows Link to try it out for free though afterwards tells Link he will have to pay to upload picture data. Symin will allow Link to upload a random type of picture that will fill in any missing entries though beyond its type the picture received is random.
Along with the Camera Rune and Hyrule Compendium the Album is one of the original default runes that existed on the Sheikah Slate that existed on the Sheikah Slate when it was owned by Princess Zelda one hundred years prior to the events of Breath of the Wild. However when Link finds the Sheikah Slate, its data is corrupted and forces him to have Purah fix it with her Guidance Stone. After its corrupted data is repaired restored, Purah discovers pictures of Hyrule as it appeared one hundred years ago, which Purah deduces where originally taken by Zelda. Purah suggests that Link was probably with her when the pictures were taken and theorizes they could be useful in restoring Link's memory, though tells him to talk to Impa as she will likely known more as she was close to Zelda. This leads to "Captured Memories" in which Link learns how to use these pictures to recover his lost memories. These pictures are permanently stored on the Sheikah Slate and cannot be deleted from the album. Interestingly, the pictures show how various places looked before the Great Calamity though their names are encrypted in Sheikah. Once Link finds the location depicted he must find a glowing spot where he can recall a memory regarding that location. Once recalled, the name of the location of the picture will be decrypted and a film icon will appear on the picture representing its coresponding Recovered Memory has been unlocked. After discovering the location of all 12 pictures and recalling their memories, Link must return to Impa who reveals a final picture that was printed and hangs on the wall of her house. This recalling the at this location unlocks Link's memory of how he was injured which lead to him being placed in the Shrine of Resurrection that Zelda and Purah's research team had uncovered. After this memory ends Link receives a telepathic message from Zelda. It is ultimately revealed Zelda left the pictures behind to help Link recover his memories. However their are five memories unrelated to "Captured Memories" Quest that are recalled during the story.
Additionally, Link can use the album to store pictures he takes from selfies to pictures he takes to complete various Side Quests. Link has a limit to how many pictures his album can store, so he must delete photos to free up space and is unable to take pictures if his album is full. Pictures in the album record the region or place where they where taken allowing Link to use it to figure out the region he is in using pictures he takes if it is not clear on the map.
Album pictures can apparently be printed using an unknown process as the 13th Captured Memory photo was printed as was the Picture of the Champions taken by Purah before the Great Calamity.
Purah's rune research
At some point during the Age of Burning Fields, at age 30 Purah began working on the Sheikah Sensor+ upgrade and was 80 years old by the time it was complete. During the development of the Sheikah Sensor+, Purah discovered the existence of other runes while studying some ancient Sheikah texts including Cryonis, Stasis, and Remote Bombs. This knowledge presumably allowed her to develop the Stasis+ and Remote Bomb+ upgrades. It also allowed her to write the Sheikah Slate Manual which contains information on Cryonis and Stasis. She also wrote the Camera Manual at some point as well, which acts as an instruction manual for the Camera Rune. At some point after this Purah began working on a reverse ageing rune which she hoped would rejuvenate herself and the other elderly Sheikah, in order to better help Link though her diary implies she had been trying to develop it before the Great Calamity to restore retired and elderly soldiers, knights, and warriors to their physical prime to bolster the Hyrulean Army to confront Calamity Ganon with the Champions and Guardians, but she was unable to complete it though eventually resumed it when she and the other Sheikah began to reach old age during the Age of Burning Fields. Purah took the risk of testing it on herself at age 126. At first the results seemed promising, reversing her age first by 70 years (putting Purah in her 50s), then by 20 (puttin Purah in her 30), then by 10 (putting Purah in her 20s), but the process then became uncontrollable causing her to regress physically and mentally to a teenager going through puberty (Purah began to obsess about a pimple and her personality was partially effected by hormones) before finally becoming trapped in the body of a six year old girl when her reverse aging finally stopped as her condition stabilized. Purah was supposedly developing a rune to reverse effects right around the time of Link's revival, though her research was interrupted by her lab's Furnace going out forcing her to continue her research by gaslight when she and Symin both fail to relight it. Presumably after Link relights the furnace, Purah is able to return to her developing a age boosting rune to reverse the effects of the reverse aging rune or prefect the reverse aging rune so that it restores her to an age she is more comfortable with. However it is implied her lab's financial situation is hindering her research efforts as she remains six years old for the rest of the game. She notes if she had a few million Rupees she could potentially develop new items and Runes for Link indicating Rune research is not cheap and requires a lot of funding as Purah has spent most of her personal savings to develop her rune upgrades and anti-aging rune.
Despite her knowledge of Runes, she makes no mention of the Amiibo Rune or Master Cycle Zero though presumably she is simply unaware of their existence.