So many sad and crazy stories!
Mine is sort of sad, because it did herald the end of my marriage, although it took me a few years to realise that this was the case. My ex-MIL was actually a gracious woman, gentle, charitable, old-fashioned, but not malicious. But she came from a very repressed, now-impoverished, once-aristocratic family and was extremely set in her ways, and not really capable to showing empathy (although she was fundamentally kind). My ex-H had her lack of empathy without the kindness.
She lived about three hours from us in the depths of beyond, in a valley that had no mobile reception. The large house was always freezing because she just didn't see the need for central heating. Now, I'm not much of a TV watcher (in fact, mostly I hate it being on for no purpose) but for her, the TV would be ceremoniously turned on once per day, for the bedtime news, listened to with respect, like an oracle, then reverently put back to sleep.
Evenings would consist of dinner: tiny portions of unseasoned food, normally consisting of an undercooked pork chop, an egg cup measure of peas, and two plain boiled potatoes. After that everyone would sit in the icy "drawing room", pretty much in silence. Wine was frowned upon, and even tea was rationed. Coming from a noisy Irish family, I found it nearly unbearable. I'd go to bed just to escape the silence. I found out subsequently that MIL had a "special bottle" of Schnapps in the kitchen that she drank from periodically throughout the day.
The bedroom we were given had two single beds in it, with antiquated blankets and counterpanes, everything thick with dust. It was so cold you could see your breath in the air. At the time, my own mother was not well, she had cancer and was in the hospital a plane ride away. I had not wanted to go to visit MIL, due to my own mother's illness, but my (now) ex had made such a fuss I felt I had no choice. MIL was baffled by my need to get a signal on my phone to keep in touch with my dad and get updates from the hospital. They had an old fashioned bakelite phone in the hall, but she had a horror of it ringing, and wouldn't let me use it. It was all so strange and the fact that my ex made me out to be the unreasonable one to be concerned about my mother while being stuck in this strange time-warp without communication was the final nail in our already moribund marriage.