Deep Power Stone

The lengendary Deep Power Stones were a royal family secret. Only the royal family knew exactly where they were as the two stones put together one way granted enormous power while put together another way would cause mass destruction. It took Robotnik a while, but he managed to translate the scrolls that told where the stones were. However, he only managed to get one, as Tails' plan on making Robotnik think that the Freedom Fighters found and destroyed the other worked. The power stones allowed Sonic and Sally to destroy the Doomsday Project.