Enlightenment

Enlightenment was the prize for which the Eternals Captain Wrack, Striker, and their rivals sought in a race 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)

In the 27th century, Enlightenment, in the form of the diamond, it was offered to Bernice Summerfield by the two Eternals Hardy and Barron. (BFBS: The Heart's Desire)