Darkness’ corruption

Darkness from the dark minions was a fragment of the power of those evil beings but it wasn't something that could grant one the power of darkness.

"Let's get out of here, El."

The mage must be someone who wanted to become a follower of evil and was helping the dark mage with something.

She did not know for certain yet, but he must also be someone responsible for the dark mage's presence in this town.

"...let's go."

From what they understood, the mage that was helping the dark mage wanted to become a dark mage and was serving him. He might have pointed him to this town, thinking it did not have many strong individuals and was an easy target.

Then when the dark mage went to deal with the town people, he must have stayed behind.

It takes a lot of sacrifices and conductors to open the windows on the other side and produce a fellow dark mage artificially.