User blog comment:The Arkham Joker/Who do you think the Arkham Knight is?/@comment-27663651-20160123211221

He is Jason Todd. He didn't get killed by Joker's torture and pistol attack. His Robin armor protected him.

When the game wasn't released, i had 5 theories:

1-) Azrael

2-) Deathstroke

3-) Jason Todd

4-) It sounds stupid but Hush

5-) A New Guy