Words of Radiance, Oathbringer|
Glys is the spren with which Renarin Kholin has bonded that affords him the Surgebinding abilities of a Truthwatcher. Their bond grants him the Surges of Progression and Illumination.
According to Jasnah, Glys is one of the Voidspren. However, Glys has actually been corrupted by Sja-anat.
Truthwatcherspren are suspected to be of Cultivation due to the Surge of Progression they afford their Surgebinders.