Explanation: The Praetorian Guard were a unit of Roman soldiers whose nominal job was to protect the Emperor from threats.
... very often, the Praetorians were the threat, and assassinated more than their fair share of Emperors through the years.
The Praetorians were not particularly good soldiers, recruited largely from Italian families, and acted as a secret police. Their position was viewed with some disdain by the regular Legions, who saw them (not entirely incorrectly) as parade-ground soldiers who got to spend their careers eating grapes in sunny Italy at pay-and-a-half and with an early retirement bonus while the real troops were off fighting on the miserable frontier.
The later Byzantine Empire, centered in Greece and claiming the mantle of the Roman Empire of old, would use a unit of Norse-Germanic troops known as the Varangian Guard to protect the Emperor - they were, notably, much more loyal and less inclined to murder their employer!