Gideon may have been dozing off but he suddenly got brought back to a distant memory in the past.
"Deon, are you ok?" Alice asks him and Gideon blinked.
Was he seeing this correctly? Is this really his sister in front of him?
"Aren't you going to explain to me what happened next?"
Oh no this... this seems like a very convincing illusion. One that is based on a conversation he and his sister had. It was his day off and his sister was staying over for the week since she felt stuffy in her dorm. If he remembered what he said back then correctly...
"The Prince sent off Kassandra to the north to aid in the fierce battle. But no one would expect Matthew himself participated in the battle. That's the chapter update so far"
The next few chapters confirmed Kassandra's death alongside many of her men. This was the start of Luciel's slow descent into madness.