What changed?

What might decided that Nero simply became bored of the opposition or his morals weakened yet further and he became more tyrannical. Nero the monster is a very simple attractive explanation.

But context is important.

The conspiracy of Piso and the swath of the Roman elite cut down in the conspiracy undermined Nero’s political position. Nero took pains to show that the conspiracy was real. But the killings raised the political stakes. Were there others looking to remove the emperor? Would the emperor strike at others whom he perceived as potential threats?

Once the Pisonians were rounded up, the killings continued.

• Poppaea was killed, rumoured to have been kicked by Nero while pregnant and dying of her injuries (Tacitus, Annales 16.6; Suetonius, Nero 35). She was treated with great honours in her funeral. In itself, her death was probably of limited political significance, but it did leave Nero yet more isolated and still in want of heir.
• Caius Cassius was banned from the funeral. A trial followed, though the charge is not reported. He was of a very eminent family, descended from the Cassius who had killed Caesar, wealthy, but also morally restrained. He honoured his ancestor, as most Romans did, and this seems enough to have have roused suspicion. He was exiled.
• His fall was coupled with that of Lucius Silanus, a man from an equally noble family. No wrong doing is reported. He was first exiled and then killed (Tacitus, Annales 16.7-9).
• The next victims were Lucius Vetus, Sextia (his mother-in-law) and his daughter. Vetus had been consul with Nero in 55 and was a very important figure in the senate. He was placed under house arrest following accusation levied by a man he had imprisoned while governor. He sent his daughter to petition Nero, but he refused to see her and she took to haunting his doors and shouting out to him. In the end, he quietly disposed of his property and all three of them killed themselves in the same room (Tacitus, Annales 16.10-11) .
• In 66, there were more deaths. Publius Anteius, a rich senator, and Ostorius Scapula, a military hero who had fought in Britain, were named as conspirators (Tacitus, Annales 16.14-15). 
• Three other figures followed: Annaeus Mela, Cerialis Anicius, Rufius Crispinus. Annaeus Mela was the father of the poet Lucan. All three were remote from the centre of power (Tacitus, Annales 16.17).
• Petronius, the novelist and formerly at the centre of Nero’s court, found that many of his household were arrested and taken in for questioning. The application of torture made it likely that some accusation would emerge and Petronius took his own life. But he did it slowly. Cutting his veins, then binding them and holding a dinner party, reciting some light verses, and then composing a letter in which he detailed Nero’s sexual depravities (Tacitus, Annales 16.18).
• Then, a Minucius Thermus, who had been praetor, was killed by Tigellinus, the prefect, supposedly in pursuit of a private quarrel.

This is long list. It shows the continued tensions of Rome and the brutality of the regime as it clamped down on supposed threats or dissidents.It was in this context that the attacks on Paetus and his circle began.

Trials

The account of the various trials in Tacitus is very detailed (Tacitus, Annales 16.21-35). Cossutianus Capito launched the attack. He was a man Thrasea had himself successfully prosecuted for corruption, but was the son-in-law of Tigellinus. His involvement suggests strongly that Nero was behind the trial.

The charges were, in essence, disloyalty to the regime. He was accused of building a faction opposed to the emperor and of failing to honour the emperor. He was accused of being a revolutionary, not actively, but in leading others towards revolt.

Thrasea consulted his friends as to whether to defend himself. Arulenus Rusticus, who was tribune, offered to veto the trial, which would have caused a major confrontation. Thrasea however proclaimed that resistance was useless, and prepared for the verdict.

Borea Soranus was accused of conspiracy. The evidence was beyond flimsy, but his daughter had consulted fortune-tellers and this added to the suspicion (Tacitus, Annales 16.30-32).

When the verdicts were announced Paetus, Soranus and Servilia, his wife, were condemned to death. Cassius Asclepiodotus was stripped of his property and driven into exile. Helvidius Pricus and Paconius Rufus were exiled were banished from Italy. Curtius Montanus was sent to his father for punishment.

Thrasea killed himself when the verdict was announced, instructing his wife to carry on living for the sake of their daughter. He was surrounded by friends, and they were unlikely to forgive or forget. Thus, Thrasea was added to the growing list of martyrs to Neronian tyranny.

What resulted from the Neronian purge?

More deaths; more violence; more fear; more suspicion. Nero had removed opponents but surely he had made more enemies.

Thrasea and Senatorial Opposition            The Generals              Death of Nero