Voidspren

Voidspren are spren that, instead of being connected to either Honor or Cultivation, are under Odium's control. They are similar to other types of spren in many ways, such as their ability to bond with things in the Physical Realm and their various shapes and habits. However, these spren fight on the opposite side of the Desolations, aiding Odium's goal to destroy the Rosharans and ultimately earn his freedom from Braize. Once they were entrapped by the Oathpact, the Voidspren would torture the Heralds present on Braize in an attempt to get them to bend the bars of Damnation and release them back to Roshar.
==Bonding==
Like the other types of bonding spren, Voidspren can only bond to certain individuals during certain times. For many Voidspren, the Everstorm is needed for the bonding process, likely because of its output of Voidlight. The lesser spren that create Regals can bond during highstorms, likely because the Regals can't invest the Voidlight. The bonding process in the previous Desolations is unknown since this is the first Desolation when Odium summoned the Everstorm.
Some Voidspren, like Ulim, are able to bond with a singer without changing their form, residing in their gemheart while leaving the other spren there. The Voidspren can leave and return from their gemheart at will, without the need for a highstorm. This will still influence the singer's emotions, though the influence will leave if the Voidspren exits their gemheart. While inside their gemheart, the Voidspren can communicate directly with the singer though their mind and even hear their thoughts.
Some Voidspren are able to enter any animal's gemheart, giving them some influence of control, depending on the animal's intelligence.
==Types==
There are many varieties of Voidspren, and each type, similar to the other bonding spren, serves a different purpose. Some of them can form bonds, and some haven't revealed whether or not they can. Raboniel has mentioned a type of spren capable of cracking ciphers, but further details about this type of spren are currently unknown.
=== Chaosspren ===
Chaosspren are normally invisible, but within Urithiru they leave sparks in the air.
===Guiding Spren===
These spren haven't shown any bonding abilities, and they serve Odium as guides and messengers. One such spren is Yixli. They appear as glowing yellow, shaped like windspren with eyes like a Shin. In order to put themselves at the height of humans or singers, they stand on a yellow pillar that rises from the ground. When they walk, another pillar will meet any moving foot, keeping them even. These Voidspren are seen guiding the multiple bands of newly made Voidbringers to settlements, cities and, in the case of Kaladin's group, to Kholinar. They are able to detect the arrival of an Everstorm before it appears. They can also choose who can and cannot see and hear them in the Physical Realm.
===Secretspren===
These spren are similar to the above spren in their color, being yellowish-white, but instead of appearing similar to windspren, these look more like "vivid yellow spheres crackling with energy." They are used during the Siege of Kholinar to locate any fabrials being used in the city. If a fabrial is turned on, these 'screamers' will wail, then start twisting over each other above the area, alerting a quickly-following Fused. The screamers can also sense when a Lashing is used, but not when a Lightweaving is created. Pattern explains that he and Shallan are quieter than Syl and Kaladin. They can detect Stoneshaping, but not a Willshaper looking into Shadesmar. They cannot detect illusions, as they burn through much less Investiture than a Lashing, and their senses are fully blocked by aluminum. They could also be blocked by certain Aviar or Allomantic copper, as they are similar to life sense and Allomantic bronze. These spren are useless within Urithiru, since the whole tower is made of fabrials and thus secretspren would have trouble locating a specific usage of Investiture.
Overall, secretspren can detect Adhesion, Gravitation, and Cohesion, but cannot detect Illumination, Transportation (at least when it is used only to look into Shadesmar), or a Shardblade being summoned.
=== Stormspren ===
This type of spren can bond with singers during a highstorm or the Everstorm, granting them Regal power of stormform. The stormspren appear as rolling lightning that moves across surfaces. Among the listeners, they are described as looking smoky, as well as giving off a "strange red light" and splinters of lightning. Despite a similarity in appearance, they are not of the same species as the spren Ulim, who can in addition take on a human appearance. 
Stormspren can be found naturally prior to the arrival of the Everstorm. Hundreds of stormspren will appear at where its lightning strikes the ground, and will linger a short while before disappearing. Their color implies that they are normal spren who have been corrupted. They were not originally of Honor, however.
=== Other Regal spren ===
Other types of lesser Voidspren are likewise capable of bonding a singer and grant Regal powers. Their appearance and regular behavior are by and large unknown, as they rest in the singer's gemhearts to provide them their powers.
==Notes==