The Cadaver Synod (Synodus Horrenda) represents one of the darkest and most surreal episodes in papal history. In January 897 AD, Pope Stephen VI ordered the disinterment of Pope Formosus, who had died nine months earlier. Formosus had been a controversial figure involved in intense political rivalries for control of the Holy Roman Empire and the Papacy.
Stephen VI, allied with the rival Spoleto faction, aimed to invalidate Formosus's acts, appointments, and papal decrees. To achieve this, the seven-month-old corpse of Formosus was dug up, clad in sacred papal robes, and seated upon a throne in the Basilica of St. John Lateran in Rome.
A deacon was assigned to stand beside the rotting corpse to answer charges of perjury, violating canon law by serving as bishop of two dioceses simultaneously, and unlawfully coveting the papacy. Unsurprisingly, the deceased pope was found guilty on all counts. The court voided all of Formosus's ordinations, stripped the corpse of its papal vestments, and chopped off the three fingers of his right hand used to perform papal blessings.
The body was then dragged through the streets of Rome and tossed into the Tiber River. The grotesque spectacle outraged the Roman populace, leading to a revolt that saw Pope Stephen VI imprisoned and strangled later that same year.