If it wasn't for VaatiVidya you'd be able to write everything I know about the plot of Dark Souls on one single post-it note.
This man is the Cliff Notes of Dark Souls and he's back again with a really, super helpful list of new mechanics in Dark Souls III. Stuff that will genuinely enhance your playthrough of the game. I highly recommend watching this.
There's a lot of interesting stuff in here that you'd be hard pushed to ever discover by yourself, so even if you're spoiler averse I'd give it a look.