Chazar,
I may not know much about the game but I do know about killing devils
So I should have told you about murdering winter. It just will not get the job done in a cost effective way since you need quite a few castings to kill devils. I have gone so far as to cast Wolven Winter 3 times followed by 2 murdering winter without effect. I figure 3 castings of muredering winter should get the job done but that is a *lot* of gems.
Re: Air Queens.
I honestly do not think that they are "all that" against devils. In test after test I have found that prot is the big killer against devils and air queens just don't get high prot due to their low base defence. Ice Devils OTOH have 15 base prot and can get up to 30 quite easily.
Something like
Shiled of Charcoal Shield, blood thorn, Some prot-15 armor, Flame Helmet, and a pendant of luck on something with a high base prot ( eg: any devil commander, an earth troll king, maybe a wraith lord, the wraith lord does not have that much but the etherial does help ) with smack them around like no tomorrow.
The heat aura is a real killer, be sure to be fire resistant.
An AQ wearing the Amon Hotep will obliterate devils. But you can only have one of those.
A golem wearing artifact armor ( monolith, Asefik's ) can survive a long time against devils but he's only useful as a tank for wrathful since he's a clutz. You could also put armor like that on an AQ with a flame helmet that should give you sufficient prot to tank and crush.
As I said above ghost riders are shocking effective against devils. Heck they are effective against everything except specially made armies or really, really good SC's.