After clearing the northern part of the Fifty-Two Territories, Davis met up with Myria who seemed to have also cleared the southern part after leading those Immortal Vacuous Beasts to the many Killing Spirit Formations she set up.
After witnessing the magnificence and usability of Spirit Formations that initially used soul force before using the heaven and earth energy to function, Davis wanted to badly learn them.
If he had learned them before, he felt like he wouldn't have much trouble and didn't have the need to exhaust himself like Myria but it was not like she didn't exhaust herself each day to build these formations, so he knew that the usage during battle was still limited.
But still, he wanted to learn as the usability for preparations was high.
However, since Myria, or rather Ellia had already given a wide range of Spirit Formations to Yotan and Threelotus, he didn't ask Myria to teach him.