It was able to seal one’s Adam’s apple and make the opponent unable to make a sound. This was a magic spell that Supreme Mages would use some time to seal their opponent’s Adam’s apple to stop them from chanting their spells and arranging magic elements to cast spells.
The only thing was that Supreme Mages usually had their magic power surging beside them for protection, so it was hard for the Mute Spell to go through this layer of protection. Unless it was used for sneak attacks when the opponent didn’t have his or her magic power surrounding them, it wouldn’t be effective. Therefore, this spell became one of those useful, yet useless spells.
Right now, Gleen Pan only had spiritual power, which was a lot weaker than magic power. When faced with Gloria’s vast magic power, he was like a naked sheep facing a bad werewolf. It was too easy for the Mute Spell to go through his spiritual power and make an effect.