If you have maintained the pacifist conduct, any Healer player monsters that generate will be peaceful.

Using genocide breaks pacifist conduct.

New monster “Phantom of War”, a powerful player monster style @ that appears on either the Astral Plane or elsewhere on the ascension run, but only if the player has successfully maintained pacifist conduct up until that point.

“Psuedopacifist” conduct - you are allowed to kill monsters, but only in self-defense. This means you cannot kill a monster which generated peaceful, even if you anger it, and you cannot kill monsters which are incapable of taking action to harm you such as blue jellies.