A Shortcut Through the Cosmere
For a traveler, a perpendicularity is less like a doorway between two rooms than an entrance to a different kind of route. Crossing one can take you from the Physical Realm into the Cognitive Realm, where thoughts and perceptions shape the landscape. In that realm, the distances between planets do not work the same way they do in ordinary space, making travel between worlds possible without crossing the vast physical gulf between them.
A traveler still needs a way back out. Another perpendicularity can serve as an exit into the Physical Realm, so these crossings act as gateways at both ends of a journey. Their locations matter: a worldhopper who knows where one forms has access to a route most people cannot use.
Power Makes the Passage Possible
The concentrated Investiture at a perpendicularity is what makes the boundary between realms crossable. Investiture is the Cosmere’s underlying magical energy; where enough gathers, the realms can overlap in a usable way. The crossing may appear as a pool or another distinct feature, depending on the place and circumstances.
That makes a perpendicularity both infrastructure and a bottleneck. It can connect otherwise remote worlds, but travelers must find and reach the crossing—and a route is only useful if there is a safe way through it.
