At one point, every Doctor Who fan has asked themselves... What is the hybrid?

Half-dalek, half-time lord? Half-human, half-mire? Half-zygon, half-human? Half time-lord, half-human? 

At the end of the universe, Ashildr concludes that the Hybrid is two beings.

Two beings that will stand Lost on Gallifrey and break a billion billion headphones with discussion and laughter. Luke and Chris.