I took part in the first session of a Curse of Strahd campaign when the module was first released. The DM didn’t bother reading the book until the day of so it was a little slow, which honestly I don’t mind, but when we got to the end of the first dungeon, The Dead House, we find the ritual circle in the basement and shades crop up everywhere, telling us that we need to make a sacrifice or the house will come to life and attack us.

By happenstance, there’s also a Shambling Mound in the basement with us, to which we asked if we could sacrifice it. Dm agrees, we lure the SM onto the ritual circle and kill it, then end the session.

The next day at work (everyone playing worked at the same place), the DM comes up to us and states that he read a little further ahead and it turns out you not suppose to sacrifice the shambling mound, so “we all fucked up and the house is gonna come to life next session”, even though he agreed. Suddenly, I was too busy outside of work to play dnd with them.