Living Myth is a system that uses flaws. These give you back character points which you can spend on other things. Some flaws require “Will checks”, which is a roll of your Will attribute against a certain number of dice. If you fail the Will check you succumb to the effects of the flaw, if you succeed you do not succumb but the difficulty is increased by one dice next time you have to make the check.
Here is a sample flaw which I thought captured the spirit pretty well, but also seemed like something worth soliciting feedback on.