Boredom

Boredom was an emotion.

The Doctor frequently claimed that he had left Gallifrey because he was bored. (TV: The War Games) However, Davros believed that this was a lie. (TV: The Witch's Familiar) The Twelfth Doctor confessed it was a lie while inside his confession dial. (TV: Heaven Sent) The First and Fourth Doctors admitted that there several other "pressing reasons" at the time. (TV: Twice Upon a Time, Logopolis)

Among the things the Doctor found boring included the studying of Druidic lore, (TV: The Stones of Blood) the Vulgar End of Time, (AUDIO: The One Doctor) the two weeks he ran Taunton for in the 18th century (PROSE: The Highest Science) and Earth in 2105. (TV: The End of the World)

Ace called Perivale "the boredom capitol of the universe". (TV: Survival)

Jack Harkness thought that the Arcans were boring. (TV: Cyberwoman)

Joanna Harris, a Vampire, said that she had not been bored since the invention of the Internet. (PROSE: Vampire Science)

Das, a Neanderthal, did not understand why humans hated boredom. (PROSE: Only Human)

The New Earth Republic was so successful that boredom was the only problem. (PROSE: Synthespians™)