Fifteen years prior to the start of the series, N Ma created the Hades Gate to send his entire army to Earth's surface in oder to conquer. The invasion was stopped by the Heavenly Saint Blagel when he sealed N Ma away, however, in turn, N Ma managed to corrupt Blagel to become his servant, turning him into Wolzard.
The members of Infershia then began working to break the seal so N Ma can spearhead their conquest of the surface world again. However, over time, some of the Infershians began to realize N Ma's true level of insanity and that his obsession with destroying Magitopia was bringing about reckless countless needless deaths, leading to some revolting against N Ma's regime.
After N Ma was destroyed, Hades Goddess Sphinx took over the Infershia to rebuild their world and start a new with Magitopia.
Homever,possibly some of them are still not comply with the new era of peace.