In fact, before seeing Fury, Roy had been thinking about how to deal with these Horsemen of the Apocalypse and what topics to attract their interest.
Since the Four Horsemen of the Apocalypse were siblings, he had thought about using the topic to the imprisoned War in the beginning. He believed that the other Horsemen would definitely take the matter of War being framed seriously.
However… Roy could not explain his source of information. Leaking plots was not something that could be done at any time. Moreover, the matter of War being framed was full of all sorts of suspicious points. Not only did it involve the Charred Council, but it might also involve the schemes and arrangements of demon kings like Samael or Lilith, so he could not touch it easily. Roy would be in trouble if he did not handle it well.
However, while chatting with Julia, the situation of Samael's demon king city, the Black Stone Throne, gave Roy inspiration!