When a knight is affected by confusion, all his controls will be inverted (so you'll go to the opposite direction that you want to go) and when the player uses a pill or a vial, it could be using another item due to the confusion but your weapons won't be affected. The player will have 3 question marks on their head during the effect.
A confusion vial is a pure white color bottle.
It symbol will be a question mark.
Monsters that can conflict confusion:
Gremlin thwacker
High-devilite
Dizzy (slime family, lichen series)
Hope it's cool :)
This idea has been brought up before, and right now I'm too lazy to use the search function for you.
Anyway, one of the biggest issues with the idea is that not everyone uses keys to control their knights. Some people use the mouse to move. What happens then?