Over the course of this day in 31, Lucius Aelius Seianus went from virtual master of the Roman Empire to strangulation at the order of the Senate. Known simply as Sejanus, he was of equestrian stock who rose to prefect the Praetorian Guard when Tiberius succeeded Augustus as Rome’s first citizen. It was not yet the “infamous Praetorian Guard”. Sejanus would make it so: his were the institutional aggrandizement — long outliving Sejanus — that would position the Guard to arbitrate imperial succession; his the persecutorial internal policing that made it a swords-and-sandals Gestapo.