Severus' relationship with the Senate was not good

One of the interesting facts about Septimius Severus is that Severus' relationship with the Senate was not good. He was unpopular with them from the start, having stolen power with the assistance of the military, and he reciprocated their feelings. On suspicions of corruption or conspiracy against him, Severus ordered the killing of a significant number of Senators and replaced them with his favorites. Despite the fact that his actions turned Rome into a military dictatorship, he was beloved among Romans for stamping out the pervasive corruption during Commodus' reign. When he returned from defeating the Parthians, he built the Arch of Septimius Severus in Rome.

However, according to Cassius Dio, after 197, Severus was significantly influenced by his Praetorian prefect, Gaius Fulvius Plautianus, who came to have nearly absolute control of the imperial administration. Simultaneously, a deadly power struggle erupted between Plautianus and Julia Domna, Severus' important and powerful wife, which had a relatively negative impact on the center of power. Fulvia Plautilla, Plautianus' daughter, married Caracalla, Severus' son. Plautianus' excessive power came to an end in 204 when the emperor's dying brother exposed him. Julia Domna and Caracalla accused Plautianus of conspiring to kill him and Severus in January 205. While attempting to plead his case in front of the two emperors, the powerful prefect was executed