The Praetorian Guard (Latin: cohortes praetorianae) was an elite unit of the Imperial Roman army whose members served as personal bodyguards to the Roman emperors. During the era of the Roman Republic, the Praetorians served as a small escort force for high-ranking officials such as senators or provincial governors like the Procurators. With the Republic's transition into the Roman Empire, however, the first emperor Augustus founded the Guard as his personal security detail.
Ryse: Son of Rome
However, during the reign of Emperor Nero, the Praetorian Guard became corrupt, many of whom became vicious, callous and cruel. Their elite status, gave them authority over the common Roman soldier and were able to get away with the most foul crimes to both the people in the occupied territories, and on their own people.
When Commodus and Basillius were made governors of Britannia, a large force of Praetorians acted as their personal bodyguards. The occupation of Britannia was known to have innocent people crucified in order to extend the message of not to defy Rome and the brutality did little more than extend the hatred of the Britons towards the Romans. The Praetorians were also involved in Commodus' fleeing York after murdering king Oswald, pushing aside the defenseless civilians and took the armored ship to flee.
While the barbarian horde headed nearer and nearer to Rome, the Praetorians were responsible for slaughtering any civil disobedience to Nero. Apparently things got so bad, hundreds of people's bodies were dumped in ditches, that sickened even the Praetorians themselves.
The Praetorians were chosen for their elite fighting capabilities and came from hardened soldiers, however due to their lack of facing an opponent that can fight back, and laziness reduced their fighting capabilities making their abilities greatly reduced. Their best attack is with their use of shield to bash against their opponent that can't be blocked.
Praetorian Guard on Wikipedia