User blog comment:Enriant/Heaven and Hell/@comment-26982641-20160602080446/@comment-26982641-20160606214539

Well, Knights cannot be only killed by First Blade IMO. Amara isn't their power source. They are just ancient demons and they even possess more weaknesses than White-eyed demons or Azazel. Alastair was way more resistant than Abaddon. A Seraph can smite Abaddon is speculation but its very possible since Knights are even lower than regular angels. And Cas only used souls to start a war. Afterwards he withstand Raphael withoutthem. Sure Raphael can easily kill him but can't smite instantly. Reapers aren't angels, even in s9, Bartholomew comfirmed that by saying your species.