This advice kind of sucks. What's the point of fighting a Kostyan or Igbah with an archon, other than to just cover your ass RP-wise? You don't have much hope of killing one of them with an archangel, but you have even less with an archon.

If/when you do have to fight someone scary, be sure to get the archon to sanc you before engaging the person. I used to use mephits for that (attacking and killing them immediately after conjuring), but that may be a no-no for some good-aligned conjurers.