We get to flashback to the events we opened the series with, but now from Demona's POV. We've already learned that she was part of Robert's plan to align with Hakon to get rid of the humans from this castle, but now we get to see more of the specifics and the ways in which Demona was involved.
It's also fascinating to me that the animation of Demona when she's with Goliath is so starkly different after Goliath leaves. There are suddenly more lines on her face. She's suddenly more gaunt, even more aged. Not in every panel, but in enough of them that it really is striking the way we're meant to see the Demona Goliath sees as innocent and angelic, his 'angel of the night.'
I can't decide if the switch is meant to clue kids in that these actions of hers are bad or if we're supposed to see this as how Demona views herself in this moment. Of course, the most, digging for meaning even where it might not be course would be to see this as how Demona sees herself. When she's scheming with Robert, a human, she sees a wickedness in her actions. Perhaps it's even a sign that there is some part of her that knows she was in the wrong here, even if she cannot address that to herself.