Probably the last man who knew how it worked had been tortured to death years before. Or as soon as it was installed. Killing the creator was a traditional method of patent-protection.
Terry PratchettHe talks pretty big for a gutter wizard," he muttered. "You don't understand at all," said the wizard wearily. "I'm so scared of you my spine has turned to jelly, it's just that I'm suffering from an overdose of terror right now. I mean, when I've got over that then I'll have time to be decently frightened of you.
Terry PratchettI saved a man's life once," said Granny. "Special medicine, twice a day. Boiled water with a bit of berry juice in it. Told him I'd bought it from the dwarves. That's the biggest part of doct'rin, really. Most people'll get over most things if they put their minds to it, you just have to give them an interest.
Terry Pratchett