He pays some mind to the flashback, garnering just a little more insight to the dark mage's character. Only a snapshot serves as his understanding of the circumstance, but his opponents are familiar with 'Mustafa's bootlicker'. It's possible that some kind of loss transformed him into what he is if the dark magic itself didn't. Moreover, if they know him as something less than a 'troublemaker', that means they are familiar with him to some extent.

"I do know," Soren replies, watching the grisly magic rot his prey to nothing. "That's why I've never been interested in studying it. You're chasing something beyond the mere extinction of your foes. I'm not like that."