Yes, there was no mistaking it, there were actual clouds in his dungeon covering the phosphorescence crystals on the ceiling. When Simon examined them carefully, he noticed that they weren't just ordinary clouds but condensation of thick amounts of mystical energy.
That is to say, the mana around the main floor had turned so dense that they formed clouds.
"What was going on?" Simon was confounded, just as he was marvelling at the changes that had occurred on his main floor, he felt a sudden presence that was quickly rushing towards him.
Simon was quickly alerted sensing how powerful it was; however, when he saw the being that released such an aura, all his guard relaxed and he couldn't help but make a delighted smile.
WHOOSH… the Blackthorn Demonic Warhorse quickly landed in front of him and greeted him with a bow of his head. Simon smiled and patted the latter "It seems you have improved dramatically since the last time I saw you".