Enlightenment Aura was one of Negris's many skills that was the most indescribable, it didn't even have a fancy name like "Truth's Murmur," which had an immediate effect.
Because the Monarch was afraid of its incessant babbling, he simply wiped its memory, which speaks volumes of the skill's power, at the lightest altering everyone's cognition, at worst rewriting history books.
However, the Enlightenment Aura had never demonstrated any concrete power. Ange had once placed the Bronze Book inside the ring of Holy Spirit Skeletons, attempting to inspire their wisdom and see if he could create a group of intelligent Undead.
Yet there was no change. The poking of eye sockets was purely a trick taught by Little Angel; the Enlightenment Aura wasn't present on the Bronze Book at the time and had no enlightening effect.