and prevent any more innocents from becoming a midday snack. Plus the circlet... can't forget the circlet ^^
That's my main reason to kill them, I've never summoned him (I'm fact, in my first playthrough I attacked him first sight. lol).
And also as you said... The circlet. The temptation is too much. My Tav will get rid of a monster and get smarter in the process!