Regill failed a save against Dominate Person in one playthrough and just gnome-murdered the HELL out of the Knight Commander. I can imagine him standing in the aftermath, covered in blood, calmly observing: "There will be a great deal of paperwork as a result of this..."
For the first time I failed the skill check during the final Hellknight trial. All the Hellknights, including Regill, immediately went aggressive.
Since I was playing a Gold Dragon with the merged Angel spellbook it went... predictably.
The best part was Regill's last words were: "Our strategy... may have been in error."