The moment the last guard fell to the ground, Marcus stood up and finished healing his wounds. Immediately after, he took the guard's corpse along with the bodies of the other five guards that were in the 1st realm and put them in his [Storage].
Unfortunately, although the corpses of the other guards in the dining hall would be incredibly useful for the creation of high-ranking undead, Marcus didn't have enough space in his [Storage] for all of them. So he only took the strongest ones.
As soon as he finished storing the corpses, Marcus left the dining hall and started running through the castle's corridors at full speed.
As far as Marcus could remember, the main dining room was on the first floor of the left wing of the castle, just on the opposite side from where he had infiltrated. However, the Viscountess's chambers were only three floors up. So whenever he climbed the stairs he would reach her.