One of the book’s most original worldbuilding elements are the spren. They appear in all kinds of sizes and shapes and are the visible expression of emotions and natural elements. There are painspren, deathspren, creationspren, as well as wind-, water-, and firespren, which personify emotions and elements of the natural world. They are described as immaterial creatures who can change shape. Those spren who are more aware or who bond with humans acquire the ability to reason and communicate. A person’s ability to do magic, transform matter, fly, and walk on walls is directly connected to the type of spren they are connected to.

In literature, embodiment and personification are central literary devices. However, they are typically understood to be metaphorical or nonliteral. Roshar is a testament to what could happen if such techniques become embodied for real. Firstly, people have a more difficult time hiding their emotions as the spren who appear reveal the pain or fear or other emotions the person is experiencing. Secondly, the visible embodiment of concepts such as honor can interact directly with people and engage in a dialogue. Many of Kaladin’s insights come during his conversations with Syl.