The Decian Dynasty was a short lived Roman imperial dynasty that ruled the Western Roman Empire between 479 and 482. I was founded Caecina Decius Basilius, Praetorian prefect under the Emperors Olybrius and Avitus of the Second Flavian Dynasty. After the death of the later, he took the Imperial Title with the help of the Praetorian Guard, rapidly gaining support of the Senate against the usurper Syagrius.
The Decian Dynasty is concidered as one of the worst imperial dynasty in Roman history. During their three years, the Empire weakened under a civil war, with the usurper Syagrius administrating most of Gaul from 479 to the end of the civil war. The Decian Emperors were characerized by their lack of military success and the division of their power due to their number (from 479 to 481, there was 3 co-emperors) and the time they passed aways from the capital, which leaved the Senate in charge, diminishing the imperial power.
Due to being totaly absorbed in the civil war, the Decian Dynasty was weak to respond against multiple barbarian invasions in the Empire, losing many territories. The most dramatic of those lost was in Italy, were the southern part of the Italian peninsula was conquered by the Vandals between 481 and 482.