Just 'cuz no one mentioned it (I'm sure you've gotten through that Demon Wall by now!), but as you fight the 2nd Demon Wall at least, y'know the torches along side the bridge? You can activate them to affect the fight in different ways. Might be helpful. At the risk of giving out spoilers, I will say no more.

It was something I noticed while I was in that encounter the second time I died. The third time I went through it was the last time I went through it.