Thay has at least two units, the Commander "Sister of Cryic" and the troop "Black Unicorn Rider" who have the trait Illusion.

Illusion requires a glamour mage to be present or the illusion dissolves. I suspect this was not intentional and that blur or something similar was intended.

If illusion was intended adding glamour paths to the Sister of Cryic would alleviate the issue I encountered when my Sister who was blood hunting with 5 Unicorn Riders as bodyguards melted when confronted by some commoners.