Complex sentence: The Doctor has also been affected by the change, however, and it's up to Ruby to deal with the cobalt bomb--which she does by flinging it into the Cybermen's base and bringing the ice tunnels down on their immobile army.
Split into simpler sentences: The Doctor has also been affected by the change, however, and it's up to Ruby to deal with the cobalt bomb. She succeeds by flinging it into the Cybermen's base and bringing the ice tunnels down on their immobile army.