Dark Ages

The Dark Ages were an era in human history following the fall of the Roman Empire.

The Rani was present during the Dark Ages at some point, extracting chemicals from the brains of humans. (DW: The Mark of the Rani)

After Sarah Jane Smith insulted Rose Tyler's age by suggesting she was still at school, her come back was asking Sarah Jane Smith if she was from the Dark Ages. (DW: School Reunion)

As the Tenth Doctor explained to Donna Noble, Charlemagne "practically dragged Europe out of the Dark Ages." (WC: The Lonely Computer)

Jorjie Turner suggested using the Space-Time Manipulator to visit the Dark Ages. (K9TV: Liberation)