u/Emergency-Option-677

So I’m in the early planning stage for a campaign I want to run in the near future where the BBEG is a seemingly ordinary man but he inexplicably has supernatural power that everybody has to do whatever he tells them to, even at their own expense, and when the players encounter him they will find out that they are somehow resistant to his effects as they have the ability to resist by making a Sanity check. Here’s what I’m thinking: if he tells them what to do, they make a sanity roll, and if they FAIL, they don’t lose any sanity but they have to do whatever he says, but if they SUCCEED they can choose to disobey at the cost of some sanity points. Is that good idea or should I change it up?