Eclipse

An eclipse was, according to what Autloc once told Barbara, when the Moon passed before the sun and caused darkness.

Aztec tradition required that during an eclipse, a human sacrifice — indeed, the "Perfect Victim" — be given to the Sun God. (TV: "The Bride of Sacrifice")

In 1794 France, the First Doctor, as part of his plan to escape from a road works overseer, claimed that there would be an eclipse, distracting the overseer long enough for the Doctor to take some money from his purse. (TV: "Guests of Madame Guillotine")

All three suns of the Planet of Light were eclipsed once every three hundred years, resulting in a brief period of darkness which caused the inhabitants to go insane with fear and destroy their civilisation. (COMIC: World Without Night)