Short answers, pulled from the story.
The Council of Constance took place from 1414 to 1418 as an ecumenical council that settled the Western Schism. It resolved a thirty-year fracture in the Catholic Church by ending the three-way struggle for papal legitimacy.
King Sigismund arrived on Christmas Eve 1414 to exercise imperial protector status over the church proceedings. He organized bishops into national blocs including England, France, Italy, Germany, and later Spain to mirror university structures.
Antipope John XXIII fled to Schaffhausen on the 2nd of March 1415 after promising to resign following an anonymous attack. Gregory XII sent legates who read his resignation before the assembly while Martin V was elected in November 1417.
The council found Jan Hus guilty of heresy during its fifteenth session held on the 6th of July 1415. A decree stated that the synod relinquished him to secular authority which sentenced him to be burned at the stake.
Haec sancta synodus appeared as a decree promulgated during the fifth session on the 6th of April 1415 asserting council superiority over popes. Frequens followed as another significant decree issued in 1417 requiring councils to convene automatically every ten years.