On the second playthrough I was trying the evil route, using the powers and resting to progress that line. And Gale did mention something about this need. He named an item but I have no idea if he ate it or not. It was not shown and he never returned to the subject. Was I supposed to do it manually somehow? I think the basement with the book was bugged and there was fire and explosions everywhere when I got there. I don't think I even had the book. Very unclear.
If you didn't answer the mirror's questions correctly it can bug out, triggering the fire traps. I had it happen on my first playthrough.
Check your party's inventories, you'll notice the book if you have it (since it has a
very distinctive icon). Having the book is only part of what you need though...
