The most characteristic symbol of the Roman Praetorian Guard is the Scorpion. It appeared on their standard and on their shields and sometimes helmets. Some of the symbols adopted by individual legions derived from the astrological birth-signs of their founders. The Scorpion is derived from the Praetorian's second founder, Tiberius.
The Praetorian Guard were the Roman Emperor's personal bodyguards. They wore special uniforms and were well paid. These guards were the only armed soldiers allowed within the city of Rome. They became very powerful and helped to assassinate many Emperors and enemies of Rome.