Enlightenment

On one occasion, Enlightenment was the prize for which the Eternals Wrack, Stryker, and others were racing across the Sol system. The prize was won by Vislor Turlough, who believed it to be a huge diamond. When he refused the Black Guardian's offer of the diamond, the TARDIS, and anything else he desired if he would hand over the Doctor, it was revealed that Enlightenment was in fact the ability to choose between good and evil, concepts of which the Eternals had no knowledge. (DW: Enlightenment)

On another occasion it was offered to Bernice Summerfield by two Eternals. (BFBS: The Heart's Desire)