I have had several instances in DND campaigns where I ran into a point of writers block and didn’t see a sensible way of bringing several narrative threads that developed on their own back together or even get them working together at all. ChatGPT has been a huge help as a sounding board for that. In doing this, it also helps to quickly get an idea of fleshing out characters further.

Whatever it replies, I usually only take it as some more inspiration and adapt it accordingly. Sometimes I use it to let it write letters and notes in the name of my NPCs though, just to get a larger variety in styles instead of everything being in my own style. Also quite helpful for that.