Devil Lines on my Forehead? (photo)

From what you've posted, it's very difficult to tell what exactly is happening. Treating the forehead with a neuromodulator over time can lessen the severity of those lines, however, if you're not visiting an experienced and well-trained injector, you might not be getting the best results and all options available to you.

In my experience, Botox alone does not work very well for diagonal lines on the forehead.  The reason for this is that those lines are not caused by muscle movement (like the horizontal lines across the forehead), but are normally caused more by the sleeping position of the head.  I would recommend using a filler in the diagonal lines.  My preference would be Belotero because this can be injected more superficially than the other fillers and can have a greater effect than something that is injected more deeply.