Well, that was stupid. Why didn't you just let Abyss defeat him on her own. What would you have done if he killed one of your people? When you had the chance to introduce an actual enemy in the form of monsters, you relented because it was too scary.
Bring one enemy human in once, and they're just as likely to forget it in generations compared to a consistent enemy.
The only reason they wouldn't is if the Author just magics it to be so. No risk, all reward, for little reason.