The Saeculum Obscurum of the Papacy is a name given to a period in the history of the Papacy during the first half of the 10th century, beginning with the installation of Pope Sergius III in 904 and lasting for sixty years until the death of Pope John XII in 964.
As a matter of fact, the dark ages of the papacy are also known as the pornocracy, the time politicking popes were mainly governed by local noblemen and prostitutes.
Sergius III is arguably the best example of the unbridled debauchery of the pornocracy. He was possibly the only pope known to have ordered the murder of another pope, namely Pope Leo V and his anti-pope Christopher, and probably the only pope to father an illegitimate son who later became pope and assumed the name John XI.