[free translation from the back cover]
The ultimate guide to create RPG worlds!
In this book you'll find the most innovative generic system, allowing limitless ideas and options. There are also rules for any setting or theme, allowing even the adjustment of the reality level of your adventures.
OPERA stands for "Observadores Perdidos Em Realidades Alternativas" (or "Lost Watchers In Alternative Realities"). It's a Brazilian generic RPG that aose from the indie scene until become published.