While Ye Yan was getting the loot from the boss' corpse, he was trying to ignore two ghosts rolling on the ground. For him, it didn't look like a fight between enemies but another kind of fight.
They look so suspicious in that position, like when you see a photo of MMA fighters on the ring taken from a weird angle in which one of them is laying on the floor and the other is between his legs with his pants a little down. You know the truth of what is happening, but the picture is too much.
When Ye Yan entered the chamber, he went straight to the spider's corpse and didn't even spare a glance at the emperor's ghost but it wasn't the same for the astronomer ghost. After Ye Yan stored the five magic source crystals that the boss dropped, the astronomer ghost entered the room, and as soon as he saw the other ghost, he rushed at him, ready to punch and kick.
For some reason, the emperor is immune to the magic power and can stay there without a problem.