User blog comment:Crimson and Darkness/Volume 25 discussion blog/@comment-34061653-20181013135327/@comment-33341107-20181014141847

The 8 minute countdown is how long he needs to be in DxD mode before he can summon Ddraig. The game rules could gove Rias the advantage but in most forms of the game Issei's team has the advantage. It could be an unseen game, but chances are no matter which game they play Ravel will have come up with a strategy to beat Rias.