>I think I got filtered by the red shadow(?) wall, in the room where the magic turret keeps shooting at you. Isn't that where you are meant to press Q and use the radiant crystal? Or is there something else?
There's a shadow wall in one of the cells near where you start as an example. The red barriers are removed by killing enemies tied to them.
>Banging the magic turret didn't seem to do anything.
You need to break the glass at the top.