Your idea inspired me:
Passive: Nearby vision changes the scaling of this character's abilities. With high vision, his abilities scale from (0-100%)of their AP scaling, and deal (0-100)% magic damage. With low vision, his abilities scale from (0-100%)of their AD scaling, and deal (0-100)% physical damage.
Q: his next auto deals 50/75/100/125/150(+90% AD)(+70% AP) *damage in an AoE.
W: he lunges in a target direction, dealing an auto to all nearby enemies. All affected enemies are dealt 10/50/90/130/170(+30% AD)(+30% AP) *damage over 3 seconds.
E: he becomes invisible for 3 seconds. At the end of that time, he releases a large burst of energy, dealing 150/175/200/225/250(+70% AD)(+90% AP) *damage in an AoE centered on him.
R: He sets down a creeping field of darkness that moves towards nearby enemies. All allies are invisible when within it, he shines brightly inside. If an enemy enters the darkness, they can see everything inside but nothing outside. When he is inside this field, he gains attack range and when he exits the field, he doesn't shine (allowing him to use his E for invisibility) and gains 15/25/35 AP.