General:
- Attacking any and all yellow dots
Not 100% accurate (on Of the Ancient, I haven't tested Devotion).
Non-hostile (yellow) Lae'zel can be killed without causing oath breaking after she's free from her cage and you refuse to let her join the party. or killed in her cage too.
The tieflings who captured her can be killed without oath breaking:
- if you haven't triggered the cutscene yet (i.e. haven't talked to any of them) and attack them at range to start the fight.
- if you select to not take side during the cutscene (use the "leave" options and reject Lae'zel). This start a fight where the tieflings are yellow and Lae'zel is red. No oath breaking for killing all of them. I believe this also happens if you fail the [Paladin][Deception] dialogue choice, but I haven't been unlucky enough to test that one.
Oath breaking only happens if you pick the "attack tielfings" dialogue options. I tested this quite a bit, making sure my Paladin started the hostilities and gave the killing blow to at least one tiefling and/or Lae'zel.