Extensions
It was not a surprise that Michael was too bored fighting ordinary Undead. Even the Anubirats and Kleshabits weren't worth his attention at this point. They weren't weak. It was just that Michael could overpower them with Sacred Constitution and the Aethyr Warhammer.
Fortunately, the Elemental Empress had fun burning everyone with her Purgatory Flame. She comprehended how to conjure Purgatory Flames, and practicing how to utilize the new flame was intriguing enough to push her to eliminate more foes. As she killed thousands of Undead, energy filled her body. She gained enough energy influxes to increase her rank slowly.
Once they were done killing the Undead in the surroundings, Michael decided it was time to kill the strongest Undead to end the reign of the Undead forces. He didn't plan on wasting his time in the Sacred Desert if he could spend his time doing something more productive.