Phil the Historian:
Old King Osmond had a long and peaceful reign, but as he grew older, he became obsessed with his own mortality. Actually, first he was obsessed with someone else's mortality, but then he switched to his own. He had heard the legend of the fabled Elixer of Immortality, and the fables of the legendary Secret of the Ages, so he summoned many knights of the realm, and commanded them to go forth and search for the key to eternal life. So desperate was he that he decreed, 'Any knight to return without the Elixer shall be executed.' So none of them came back, and he died in due course. It was not one of Oswald's better decrees.