After his rebirth, Amberser hadn't personally taken part in combat for a long time.
As the spirit of the Magic Mirror, Amberser's magic power was provided by all the Magic Mirrors, while also maintaining the Krypton Gold spell casting ability of the Golden Throne.
For the first time facing Demons, Amberser took a two-pronged approach for the sake of caution.
It turned out that Amberser's prudence was justified; these Demons showed puzzled expressions as soon as they entered the Illusion Realm.
If they had been completely befuddled, they wouldn't have realized they were under the influence of an illusion technique.
The Demons' change in expression was due to an instinctual sense that something was amiss.