Surprised to see noone discussing this, considering AI Dungeon 2 was trained using ChooseYourStory as a training dataset.
It's basically a choose your story adventure like the ones here, except you can write whatever you want as an input, and the AI tries to generate a valid continuation, using a cutting edge text generation AI.
It ain't perfect; for one, its memory only goes back 2000 "tokens" (which is roughly half a word) though you can add more information in a "memory" field. It doesn't make perfect sense 100% of the time, though it may surprise you. And finally, it seems to use a lot of names of things from Rogues and other popular CYS stories...
Sooo many times, my character turns out to be from Teckleville, or is questing to defeat a Great Lich Lord, or whatnot...
You can try it out here: https://play.aidungeon.io/