13 events the sources record for this year, grouped by region.
What happened
China (1)
Scholars were ordered to correct the texts of the Five Classics, to carve them on stone, and to erect them outside the gate of the Imperial Academy. (Book of the Later Han (Hou Hanshu), Annals 後漢書卷8 孝靈帝紀 熹平4年)
West Asia (3)
Cassius revolted in Syria; Marcus, alarmed, summoned his son Commodus from Rome and had him assume the toga virilis; Faustina is said to have urged it (Cassius Dio, Roman History 72(71).22.1)
On a false report of Marcus's death, Cassius immediately proclaimed himself emperor; even after learning the truth he quickly seized the lands south of the Taurus (Cassius Dio, Roman History 72(71).23.1)
He pardons the citizens of Antioch who sided with Cassius; on the way to Syria he refused to visit Antioch and Cyrrhus, but later visits Antioch (Historia Augusta Marc. 25.8, 25.11, 25.12)
Southern Europe (9)
After the Iazyges' defeat, King Zanticus came before Marcus as a suppliant and received the same treaty as the Quadi and Marcomanni, returning 100,000 captives and providing 8,000 cavalry (Cassius Dio, Roman History 72(71).16)
Marcus addressed the soldiers about Cassius's revolt, lamenting fate rather than showing anger, and said he would forgive Cassius (Cassius Dio, Roman History 72(71).24)
Cassius was struck down on foot by the centurion Antonius and died; his severed head was sent to the emperor (a revolt of 3 months and 6 days) (Cassius Dio, Roman History 72(71).27.2)
Marcus refused to look at Cassius's severed head and ordered it buried (Cassius Dio, Roman History 72(71).28)
Empress Faustina died, said to be from gout, though some say she sought to avoid exposure of her complicity with Cassius (Cassius Dio, Roman History 72(71).29)
As Marcus is about to make Marcomannia and Sarmatia provinces, Avidius Cassius proclaims himself emperor in the East (said to be Faustina's wish, or because he spread a rumor of Marcus's death) (Historia Augusta Marc. 24.6, 24.7)
Marcus abandons the war and sets out against Cassius; Rome is gripped by fear, but Cassius is soon killed and his head sent (Historia Augusta Marc. 25.1, 25.2)
In the East, Cassius proclaims himself emperor (said to be Faustina's wish, in despair over Marcus's illness) (Historia Augusta Avid. 7.1)
Cassius is killed with the consent of everyone but the people of Antioch (Historia Augusta Avid. 7.8)