Phaneron

Question: Why did Stryver leave Daggett at Bane's mercy? It's even more puzzling since Daggett even ordered Stryver to stay and guard him.

EK8829

Answer: Either Stryver knew Bane was going to kill Daggett and he didn't want to risk his own life by interfering, or he was simply so intimidated by Bane that he chose to comply with Bane's demand rather than draw his ire.

Phaneron

Answer: Bane actually freed the prisoners at Blackgate Prison, not Arkham. The Joker's whereabouts are never revealed, but the novelization states that he is the lone inmate at Arkham. Realistically, the Joker probably would have received the death penalty for his crimes sometime between the 8 years that have passed between films.

Phaneron