Today is the anniversary of the twelfth session of the Council of Constance which deposed Pope John XXII, of the Pisan line, one of the three claimants to the Papal throne.
There are online lives of the Pope at Antipope John XXIII and from the old Catholic Encyclopaedia at Antipope John XXIII
He had already fled from Constance, seeking thereby not only his own liberty but perhaps to thereby invalidate the Council. In both he was uncuccessful.
During his absence John was deposed by the Council, and upon his return he was tried for heresy, simony, schism and immorality, and found guilty on all counts. Gibbon As Edward Gibbon, with typical Enlightenment cynicism, famously wrote, "The more scandalous charges were suppressed; the Vicar of Christ was accused only of piracy, rape, sodomy, murder and incest."
The following paragraphs are adapted from an internet source:
Following this the ex-Pope, once more Baldessare Cossa, was promptly imprisoned in Germany and was just as quickly ransomed by his friend Giovanni di Bici di Medici of Florence. Powerful, cunning men often attract the interest and friendships of other powerful and cunning men and the father of the Medici fortune had become a friend of Baldassare during the young man’s time in Bologna. Giovanni di Bici di Medici had an eye for making money and Baldassare had a perpetual love and need of it. Bici must have seen the path that Baldassare was forging for himself, often with brute force, and a friendship evolved. As a supporter of Baldassare, Bici had loaned his money in an astute way at an important point in the career of the future Pope John XXIII and his reward from his friend in 1413 was for the Medici Bank to obtain the Curia account - a near monopoly of the bank account of the Papal Estates. It was a piece of business genius that laid the foundation for the wealth and power of the Medici in Florence that lasted almost 300 years.
The only tomb in the magnificent Baptistery in Florence is that of Baldassare Cossa. It was commissioned by the executors of his will after his death on December 22, 1419 and completed during the 1420s. The cost of this tomb was reputed to be 800 Florins - at a time when a rich man could build an entire palazzo in Florence for 1,000 Florins. The tomb was paid forby the Medici’s to say express their gratitude; engaging the great Donatello who sculptured the figure of Baldassare whilst Michelozzo created the surrounding drapery and tabernacle. It is a masterpiece in its own right, which outraged Pope Martin V who protested in vain against the inscription on the sarcophagus: "John the former Pope".
Image and text (adapted): perfectraveller.com