Ember Blight is a disease caused by exposure to corrupted Ember. Four characters are known to have been afflicted: Alric, the Alchemist, the Vanquisher, and the Destroyer.
Symptoms
The most notable symptoms of Ember Blight are mental unwellness, obsessions, and delusions, which worsen as the affliction progresses. This manifests in Alric as an allegiance with Ordrak, and in the Alchemist as a dead-set goal to destroy all Ember in spite of the consequences.
Taking Notes indicates that there are physical symptoms as well, but said symptoms are not specified outside of physical deformities.