Blinding Light +3 points per model. (+8 Inner Circle)
Before you charge with the Knights roll a d6.
A roll of one means there is no sun (it's raining or overcast) and so the Blinding Light cannot be used this charge.
Any other result means there is enough sun light for the Knights to dazzle their enemies as they charge. The enemy unit being charged which opts to stand and fire is at an additional -1 to hit due to the light being directed into their face.