Simon returned the book on the Sword Daemon's Sword Art back to the spatial ring, then he looked at the ominous black book and the Sword Daemon's mask.
By all means, the black book which emitted an ominous aura was meant to make Simon to feel more wary about it compared to the Sword Daemon's mask.
However, he was actually more worried about the mask of the Sword Daemon than the black book.
The reason why the black book was ominous was because it radiated the aura of the chaos plane and something else mixed into it.
However, the Sword Daemon's mask was an artifact of the Sword Daemon, and he would not be surprised if a fragment was still alive in the mask.
It wouldn't be the first he had encountered artifacts of supposed dead gods which still contained a fragment of their soul.
Simon was worried about the possibility of the Sword Daemon trying to take over his mind if a portion of him was still in his mask.
"Well, I'll find out soon enough."
