Doctor Who: 10 Big Questions After The Witch's Familiar

Seemingly versed in Gallifreyan lore, Davros recounted the legend of the hybrid and in The Witch's Familiar we certainly saw this come true as a tricked Doctor fused his regeneration energy with the Daleks and Davros, inadvertently creating a rejuvenated, more powerful enemy in the process.  

But then Missy saved the Doctor and Davros's plan never reached the full heights of its potential. With the Dalek city overrun with the regenerated Dalek slime of their dead comrades they were never able to emerge as an even more powerful race in the galaxy. Which begs the questions, were they the hybrid or is it something else?

Whether this legend was key to this story alone or the larger mythology of the show remains to be seen, but knowing Moffat it is tucked away ready to come back as a major twist further down the line.