I think there is so much exciting character stuff to ponder we haven't really looked at what Davros and the Daleks are actually up to with all of this. The Doctor says that the stolen planets form a giant engine. Davors says in the episode that the crucible is ready and later they discuss the humans selected for testing. What are they doing to the humans, testing them for what? Are these Mengele-type experiments, seeing what a human can endure and how it reacts or is there another purpose behind them? More human daleks or something more insidious. Will the fires of Pyrovilia help fire up th engine and heat the crucible that holds the human test subjects? Or is this all simply a huge machine designed to end the universe? What do you think?