Doctor Who: 10 Storylines That Will Never Be Revisited
6. The Fate Of The Great Intelligence
The Great Intelligence first appeared in a Second Doctor story in 1967, but the villain was most recently seen during the Eleventh Doctor's era, where it was voiced by Sir Ian McKellen and played physically by Richard E. Grant.
The entity's ultimate goal was to hijack the Doctor's timeline so it could erase all his past victories, essentially dooming the universe to a dark fate. The Doctor has saved billions of lives, so if all that good was then undone... billions would suffer and die.
Surprisingly - for a Doctor Who villain - this plan actually succeeded when the Great Intelligence stepped into the Doctor's time stream on Trenzalore, allowing it to explore the Doctor's history and cherry-pick moments of glory to turn into moments of failure. However, Clara then jumped into the time stream too, rectifying all the mayhem that the Great Intelligence caused. But the villain was never actually "killed".
What actually happened was that it was torn into millions of different versions of itself and scattered throughout the Doctor's timeline. Even though Clara was able to then save the Doctor, there are still technically an untold amount of "Great Intelligences" lurking in the Doctor's past, present, and future. Clara wouldn't have been able to kill that (how can you kill that?), so what is the Great Intelligence doing right now?
Like with Kovarian, there's no way that a villain who hates the Doctor so much would just lay dormant, but at the same time, it feels like the Great Intelligence simply ran its course in terms of being an interesting adversary for the Doctor to face.