Chapter 49 "Howling of the Dead Soul", The Time of Tranquility

Although the victim was frightened into fleeing.

For safety's sake, Ronan still left the city.

Outside the city in the wilderness, he found a secluded spot bathed in moonlight and continued to go through the remaining items.

There were four Wizard Books, one full of various Undead Wizard and Monster legends, seemingly a collection of stories for entertainment.

One book about Magic Potion, much more detailed than the one Ronan had left in the tree house.

The other two contained records of three Undead Spells, two low-level Zero Rank [Corrosive Missile] [Skeletal Spike], and one Intermediate Zero Rank - [Howling of the Dead Soul].

Ronan studied the latter for a long time, discovering that it mainly dealt with how to manipulate the Undead to emit sound waves to affect the opponent's spiritual spellcasting.

No wonder this Black Robe had a ring, a Magic Tool for harboring Ghosts.

He probably didn't understand it well, which is why he hadn't worn it for use.