https://www.cnet.com/news/the-internet-reacts-to-game-of-thrones-having-the-darkest-battle-scene-of-all-time/

There were a few instances of light. Fire from Dragons, for instance, and Melisandre setting every sword on the realm alight like your mom handing out sparklers on the fourth of July. That was pretty good.

The episode is done and you can watch the trailer for next week's episode here. Can confirm the darkness continued and persisted throughout pretty much the entire episode, outside of a few key moments where fire -- either from the mouths of dragons or the magic of Melisandre -- erupted on screen.