Ars Arcanum

Chapter 107 is an appendix entry titled "Ars Arcanum" that provides an out-of-narrative scholarly compilation of information about Roshar's magical systems, including the Ten Essences and Surges, fabrial creation and types, and detailed explanations of Windrunner Lashings and Lightweaving abilities.

This chapter consists of scholarly notes apparently compiled by Hoid or another researcher documenting the fundamental magical systems of Roshar. It begins with an explanation of the Ten Essences and their historical associations with Vorin symbolism, the Double Eye of the Almighty, and the Knights Radiant orders, while noting uncertainty about how Voidbinding and the Old Magic fit into this framework. The Ten Surges are then detailed as the fundamental forces granted to the Heralds and Knights Radiant through their bonds: Adhesion, Gravitation, Division, Abrasion, Progression, Illumination, Transformation, Transportation, Cohesion, and Tension. The text then catalogues five groupings of fabrials—devices powered by Stormlight that appear to rely on enslaved spren. Augmenters enhance forces and sensations, while Diminishers produce opposite effects. Conjoiners use rubies to create paired gemstones that produce parallel reactions across distance, as exemplified by spanreeds, while Reversers use amethysts to create opposite reactions in paired halves. Alerters, the sole warning fabrial type using heliodor stones, warn of nearby objects or phenomena with range determined by Stormlight infusion. The chapter then provides extensive technical documentation of Windrunner abilities: Basic Lashings manipulate gravitational pull to allow running on walls or creating weightlessness; Full Lashings bind objects together using Adhesion through Stormlight infusion; and Reverse Lashings grant objects gravitational pull to draw other objects toward them. Finally, Lightweaving is described as a form of Surgebinding manipulating light and sound to create illusions with a powerful Spiritual element requiring both mental clarity and emotional connection to the desired creation.