"Who would now want the golden age of Saturn?
Ours is a diamond age - of Nero's pattern."
St. Apollinaris Sidonius, Bishop of Auvergne fifth Century AD.

After the vicennalia at Nicaea, Constantine went back to Rome in January 326AD. The people of Rome were angry that he had held his celebrations outside the City against tradition.
So he held the celebrations again for them.
On this visit with him were his mother Helena, his wife Fausta, his half sister Constantia, her stepson Licinianus, and his own son Crispus.

Tentions were high amoung them.

In Helena's eyes Fausta was the daughter of Maximian, adoptive father of Theodora who had taken her husband from her nearly forty years before.
Fausta hated the elevation of Helena to the rank of Augusta, her own title, during the celebrations in Nicaea.
Constantia still lamented the death of her husband Licinius, two years dead, despite Constantine swearing to save him. Her son was now out of a chance of Imperial glory by them being bestowed upon Crispus instead.

Crispus was worried that Constantine bore a grudge against him for his victorius display at the battle of the Hellespont, although he got no rewards for it, and for his growing popularity with the people and army which was exceeding Constantine's populartity.
His command in Gaul was stripped from him and given to the the Emperors young son Constantine II.
The 326 Consulate was given to the even younger Constantius despite Crispus being the favourite.
On the return to Nicomedia in February they passed the city of Serdica (todays Sofia in Bulgaria) were Crispus and Licinianus were arrested.

Three days later they were executed at Pola (Pula).

Shortly followed by the murder of the Augusta Fausta in the Calidarium of the Bath House, whether by stabbing, scalding or suffocation is not recorded.
Eutropius mentions that this massacre was extended to his friends as well.

Aurelius Victor says that Fausta encouraged Constantine to get rid of Crispus, that she deliberately made up slanders against the Caesar.
She had lusted after Crispus, he rejected her.
When the Emperor learned the truth of this from his mother he was distraught and could only solve this awfulness the way he could, by murdering Fausta for this conspiracy.