a fiery spirit steed  

These things make great enchanter pets. You'll need the spell Command of Druzzil, which allows you to charm up to level 64 mobs. Tash, Charm, buff with haste etc., and you'll be able to dish out damage very nicely.

Unlike most of the other yard trash roamers in the Plane of Fire, these seem to have a higher max hit (721) and they bash as well, which makes them nice vs. the chaplains in the castles. Once charmed, run over the wall into the first castle, do Summon Companion, and start hunting. I have been making about 12 to 14 AA points per hour doing this at level 65.

When charm breaks, things can get a little tense, but if you keep your runes up and Word of Morell and Color Cloud loaded you'll usually be okay. If you don't like living that dangerously you can always bring a healer merc or a friend with you at the cost of about 4 to 5 aa per hour. Of course, that might be offset by never having to worry about wiping out.