Nevertheless, though the senatorial order came to hate and fear him, the evidence suggests that he remained popular with the army and the common people for much of his reign. He made lavish shows of gifts (recorded on his coinage) and he staged and took part in spectacular gladiatorial combats.
One of the ways he paid for his mass entertainments was to tax the senatorial order, and on many inscriptions, the traditional order of the two nominal powers of the state, the Senate and People ("Senatus Populusque Romanus") is provocatively reversed ("Populus Senatusque...").
At the outset of his reign, Commodus, aged 19, inherited many of his father's senior advisers. He also had five surviving sisters, all of them with husbands who were potential rivals. Four of his sisters were considerably older than he; the eldest, Lucilla, held the rank of Augusta as the widow of her first husband, Lucius Verus.
The first crisis of the reign came in 182, when Lucilla engineered a conspiracy against her brother. Her motive is alleged to have been envy of the Empress Crispina. Her husband, Pompeianus, was not involved, but two men, alleged to have been her lovers, attempted to murder Commodus as he entered the theatre.
They bungled the job. They were seized by the emperor's bodyguard, and executed; Lucilla was exiled to Capri and later killed. Pompeianus retired from public life. One of the two Praetorian Prefects, Tarrutenius Paternus, had actually been involved in the conspiracy, but was not detected at this time. In the aftermath, he and his co-Prefect Sextus Tigidius Perennis organised the murder of Saoterus, the hated chamberlain.
Commodus took the loss of Saoterus badly, and Perennis now seized the chance to advance himself by implicating Paternus in a second conspiracy. Executions followed. Perennis took over the reins of government and Commodus found a new chamberlain and favourite in Cleander, a Phrygian freedman who had married one of the emperor's mistresses, Demostratia. Cleander was in fact the person who had murdered Saoterus.
After those attempts on his life, Commodus spent much of his time outside Rome, mostly on the family estates at Lanuvium. Though physically strong, he was mentally lazy, and his chief interest was in sport: taking part in horse racing, chariot racing, and combats with beasts and men, mostly in private but also on occasion in public.
In Britain in 184, the governor Ulpius Marcellus pushed the Roman frontier north to the Antonine Wall, but the soldiers revolted against his harsh discipline. Perennis had all the legionary legates in Britain dismissed.
On 15 October 184 at the Capitoline Games, a Cynic philosopher publicly denounced Perennis before Commodus, who was watching. He was immediately put to death. According to Dio Cassius, Perennis, though ruthless and ambitious, was not personally corrupt and generally administered the state well.
However, the following year, a detachment of soldiers from Britain (they had been drafted to Italy to suppress brigands) denounced Perennis to the emperor as plotting to make his own son emperor. They had been enabled to do so by Cleander, who was seeking to dispose of his rival. Commodus gave the soldiers permission to execute Perennis and his wife and sons. The fall of Perennis brought a new spate of executions. Ulpius Marcellus was replaced as governor of Britain by Pertinax; brought to Rome and tried for treason, Marcellus narrowly escaped death.
Cleander took power into his own hands and enriched himself by selling public offices: he sold and gave entry to the Senate, army commands, governorships, and even replacement consulships, to the highest bidder.
Unrest around the empire increased, with large numbers of army deserters causing trouble in Gaul and Germany. A revolt in Brittany was put down by two legions brought over from Britain. In 187, one of the leaders of the deserters, Maternus, came from Gaul intending to assassinate Commodus at the Festival of the Great Goddess in March, but he was betrayed and executed.
In the same year, Pertinax unmasked a conspiracy by two enemies of Cleander. As a result, Commodus appeared even more rarely in public, preferring to live on his estates. Early in 188, Cleander disposed of the current praetorian prefect, and himself took over supreme command of the Praetorians at the new rank of "a pugione" ("dagger-bearer") with two praetorian prefects subordinate to him. Now at the zenith of his power, Cleander continued to sell public offices as his private business. The climax came in the year 190, which had 25 suffect consuls—a record in the 1,000-year history of the Roman consulship—all appointed by Cleander (they included the future Emperor Septimius Severus).
In the spring of 190, Rome was afflicted by a food shortage, for which the official actually in charge of the grain supply managed to lay the blame on Cleander. At the end of June, a mob demonstrated against Cleander during a horse race in the Circus Maximus: he sent the praetorian guard to put down the disturbances, but Pertinax, who was now City Prefect of Rome, dispatched the "Vigiles Urbani" to oppose them.
Cleander fled to Commodus, who was at Laurentum in the house of the Quinctilii, for protection, but the mob followed him calling for his head. At the urging of his mistress Marcia, Commodus had Cleander beheaded and his son killed. Other victims at this time were the praetorian prefect Julius Julianus, Commodus's cousin Annia Fundania Faustina, and his brother-in-law Mamertinus. Papirius Dionysius was executed too.
Commodus continued to rule through a cabal, which now consisted of Marcia, his new chamberlain Eclectus, and the new praetorian prefect Quintus Aemilius Laetus, who about this time also had many Christians freed from working in the mines in Sardinia. Marcia is alleged to have been a Christian.
During 191, the city of Rome was extensively damaged by a fire that raged for several days, during which many public buildings including the Temple of Pax, the Temple of Vesta and parts of the imperial palace were destroyed.
Commodus presented himself as the fountainhead of the Empire and Roman life and religion. He also had the head of the Colossus of Nero adjacent to the Colosseum replaced with his own portrait, gave it a club and placed a bronze lion at its feet to make it look like Hercules, and added an inscription boasting of being "the only left-handed fighter to conquer twelve times one thousand men".
The emperor also had a passion for gladiatorial combat, which he took so far as to take to the arena himself, dressed as a gladiator. The Romans found Commodus' naked gladiatorial combats to be scandalous and disgraceful. It was rumoured that he was actually the son, not of Marcus, but of a gladiator whom his mother Faustina had taken as a lover at the coastal resort of Caieta. In the arena, Commodus always won since his opponents always submitted to the emperor. Thus, these public fights would not end in a death. Privately, it was his custom to slay his practice opponents. For each appearance in the arena, he charged the city of Rome a million sesterces, straining the Roman economy.
Military officials in Rome were enraged at his behaviour in the arena. Often, wounded soldiers and amputees would be placed in the arena for Commodus to slay with a sword. Citizens of Rome missing their feet through accident or illness were taken to the arena, where they were tethered together for Commodus to club to death while pretending they were giants. These acts may have contributed to his assassination.