Watch Da Vinci’s Demons Online. The Duke of Milan is assassinated on 26 December 1476. Leonardo da Vinci has designed a flying machine that works, and a pigeon that flies without wires. The Pope Sixtus IV is revealed to have homosexual relationships. Leonardo sells his designs of air planes, automatic load canons and tanks. Leonardo begins building a war-machine for the Medicis, a mortar of sorts, and his first attempt fails. However, Lorenzo gives him a week to fix it. Meanwhile, Leonardo also continues his search for the Book of Leaves. The Pope sends his nephew to investigate Leonardo and learn more about his prowess.