Perpendicularity

"At these points, Physical matter, Cognitive thought, and Spiritual essence become one--and a being can slide between Realms."

- From Khriss's essay on the Drominad system

A perpendicularity is a stable junction between the Physical, Cognitive, and Spiritual Realms. They are used by worldhoppers such as Hoid to go from planet to planet. They are formed through the concentration of Investiture. Because of this, they are most commonly found at places where a Shard's power is focused, often in the form of a pool of liquid. A Shard can control where their perpendicularity manifests.

Mechanics
Perpendicularities are formed at locations with a large concentration of Investiture. The concentration of Investiture brings the three realms closer together and allows travel between them. The proximity of the realms also makes Soulcasting easier. They occur naturally when a Shard spends lots of time on a world. Generally, leaving a planet would cause the Shard's perpendicularity to disappear. As a result, their presence is often used to indicate the presence of a Shard. Special circumstances, however, can prevent the perpendicularity from disappearing, and there is at least one Shard that fits these circumstances. Aluminum can be used to take liquid from a perpendicularity, and it will stay Invested. They can be used to see into the Spiritual Realm. Nightblood is able to collapse a perpendicularity. Some perpendicularities are more Invested than others. The enormous concentration of Investiture in a perpendicularity makes it possible to become a Cognitive Shadow by entering one.

Known Perpendicularities

 * Scadrial
 * Ruin: the pool below the Pits of Hathsin was Ruin's perpendicularity; it was the main path used by inter-world traders before it was destroyed by Kelsier.
 * Preservation: Preservation's perpendicularity was the Well of Ascension. It served as Ruin's prison, making it extremely dangerous.
 * Harmony: Whether Harmony has a perpendicularity, and whether it's one or two perpendicularities, has not been revealed. An article in The House Record mentions a woman coming across a perfectly blue pool somewhere in the mountains in the Southern Roughs, and a sudden appearance of a strange figure by the pool. It's possible, though not confirmed, that this could be Harmony's perpendicularity.


 * Sel
 * Devotion: The Pool near Elantris is Devotion's perpendicularity.
 * Dominion: There is a second perpendicularity on Sel, presumably of Dominion.


 * Threnody
 * Threnody does not have a stable perpendicularity, but rather a number of unstable, unpredictable ones of a morbid origin. They may possibly have something to do with the creation of Shades, although the fact that the Shard of Ambition has died near the system has far greater influence on their creation. It is more of a circumstance than a location.


 * First of the Sun
 * First of the Sun is notable for having a perpendicularity, presumably Patji's Eye, without a Shard in residence. However, Patji is an avatar of Autonomy, which is likely the cause of the perpendicularity.


 * Roshar
 * Cultivation: Cultivation's Perpendicularity is located in the Horneater Peaks, under the surface of one of the Horneater Oceans. For worldhoppers of Roshar, it's the main method of travelling between Roshar and its subastral, Shadesmar. Most recently, it has been besieged by the Fused.
 * Honor: Honor's Perpendicularity is well-known among worldhoppers and spren to be unstable and dangerous. The exact pattern of its appearance is uncertain, although Dalinar manages to open it upon swearing the Third Ideal of the Bondsmiths. The perpendicularity closes on its own within a few minutes.
 * The Surge of Transportation temporarily creates a miniature perpendicularity, allowing an Elsecaller or Willshaper to travel into Shadesmar from anywhere. However, returning back to the Physical Realm presents a far greater challenge, and can only be performed in some places. It is unclear if this allows travel to the Spiritual Realm.


 * Nalthis
 * Endowment: The location of Endowment's perpendicularity is unspecified. It is, however, located somewhere in the jungles of Hallandren. The Tears of Edgli owe their existence and their unusual properties as dye material to soaking up the Investiture flowing up from the perpendicularity. There are enough cosmere-aware people on Nalthis for there to be customs at this perpendicularity.


 * Yolen
 * There is something similar to a perpendicularity on Yolen, despite the lack of a Shard.