|“||At these points, Physical matter, Cognitive thought, and Spiritual essence become one - and a being can slide between Realms.||”|
Perpendicularities are used by Worldhoppers such Khriss and Hoid to travel between worlds. They are formed through the concentration of Investiture in the Physical and Cognitive Realms. As a result, most are commonly found at Shardpools.
The pool below the Pits of Hathsin was the main perpendicularity before it was destroyed by Kelsier. The other known perpendicularity, the Well of Ascension, was extremely dangerous during the imprisonment of Ruin.
The Shardpool of Devotion is currently the only known perpendicularity on Sel.
Perpendicularities on Threnody are unstable, unpredictable, and have a morbid origin.