How do I use blend mode in order to achieve a cave FX

I was using this gradient with the blend mode "destination in" in a layer with force own texture but I need to move every single element to this layer in order to work for everything on the screen, which would be a ridiculous amount of work to move everything to it's respective layer after leaving the cave, and i'm not even counting the Z order. So there should have an easier way to do it, isn't it?

Thanks!

There is. Set that layer to Transparent>No and then change the background to black.

There is. Set that layer to Transparent>No and then change the background to black.

Thanks