Go Get a Roomie!

Percy: Elaborate on discoveries.

Panel #1
...To be perfectly honest, you haven't solved any mysteries, per se...

But when you held up these pages to the light, they provided some interesting patterns.

They all had coherent words and phrases, but were blacked out and highlighted, as if censored by some unknown entity. However, the paper itself didn't feel inky; perhaps it was black to begin with?