In the old creatures and treasures, two types of attacks were described, level attacks and chance/luck. A level attack is simple enough; make this rr every round or turn to stone. A chance attack says; roll over this number every round or turn to stone, no mods.
So if you have a pit trap, it could be make an rr, for every 10 pts of failure, take a C krush crit. OR it could be roll d100, and if you roll over 30, you miss the trap. Roll 30 or less and DIE (or take 1d10 C krush crits, or what ever).
Anther option that I like is to assign a rr, generally with a high attack level, say 25th (high attack level varies depending on party levels)or turn to stone. They may recieve a mod to the rr equal to the penalty they are willing to take in combat (for keeping eyes closed, not looking, etc), up to +100. A level one PC needs a 95 to resist a level 15 attack, and I try to make the attack level just high enough were the -100 for being blind will almost guarantee suceess...almost. PC's are notorious at fumbling. A failed or fumbled roll means the PC opened his eyes for just second, poor soul.
One other thing, when a PC is hit, they should have to make a new rr to avoid not opening their eyes and taking one to many hits of mary jane, if ya know what I mean.
Best part of this, the baskilisk in the books are tough, but have very low OB's. You won't have to change any of the monsters stats and you will be SO ammused as the party stumbles around blind trying to wack a lizzard. Hilarity will ensue.
Or mod the theme. A chance based save requiring 40 or higher to resist with a bonus of +10 to the roll for every level in crit reduction the PC is willing to suffer. If you're mean, rather than a large foe, just have the beast reduce crits by two already.
Go with fun, but leave it dangerous. Players rarely notice when a danger is statistically on their side since they worry so much about death and dismemberment, which always makes me thinks of a garbage man complaining about the smell of garbage. I mean seriously, it goes with the job.
lynn