Turn the tables a in a twisted way.
He relies on not being seen so have him in a situation where he can't rely on his own vision.
Set up an objective he has to get to through areas of:
1: darkness, where a misstep can be harmful or even deadly
2: he can't look directly at the creatures he's trying to bypass, a group of basilisks
3: there are illusions all over the place and it is hard to tell what is and isn't real, hiding from the illusionist won't be so easy since the illusionist knows the illusions well enough that they won't act as camo to his eyesight
4: combinations of all of the above
Sure, he has lots of advantages right now, but some situations don't lend themselves to those advantages as well as others. Offer up some of these other situations. If he is with a full party, make sure to put in counters to some of their abilities along with these so that they all feel challenged and might not be able to fully compensate for each other's weaknesses.
He relies on making others sight fail, make his sight less useful or downright dangerous to him. Karmic balance and all that you know ...
