In the 1974 Doctor Who serial Planet of the Spiders, the powerful object sought by the Great One is the Blue Crystal. The serial uses ideas associated with mysticism, spiritual discipline, and dangerous power rather than presenting a direct adaptation of Hesiod’s Pandora story.
Planet of the Spiders is the final regular story featuring Jon Pertwee as the Third Doctor. Its plot follows the Doctor’s confrontation with the Eight Legs, intelligent giant spiders from Metebelis III, and the Great One who seeks the crystal’s power.
The Blue Crystal is important because it links Earth, the Doctor’s earlier actions, and the spiders’ ambitions. Doctor Who frequently reworks mythic or philosophical concepts into science-fiction plots, so title associations can be misleading when compared with ancient sources.
The serial was broadcast in six parts in 1974. It also provides the transition from Pertwee’s Third Doctor to Tom Baker’s Fourth Doctor, making it significant in the programme’s production history.