How do you defend against an Abysian devil rush?

[ioticus]

I fought his main force at one of my watch towers and I can confirm he had 10 Devils and 50 Lava Warriors at turn 20. I did destroy most of his force (his Vampire Queen and 4 Lavas survived), but at great cost to my self. I lost all 9 Mammoths and 67 (of 74) wingless and Raptors, and 2 Seraphs. The only thing that really saved me is the Mammoths attacking his rear which killed 3 of his commanders and my Pretender, a strong Prince of Death, casting death spells (though he did get a "weakened" affliction in this battle.) As expected, my Raptors committed suicide by attacking his Lavas directly. They simply evaporated. I must learn to use them correctly. I don't think I can hold out. I'm on a small map and I'm sure he's cranking out at least 1 Devil per turn and who knows how many Lavas.

By the way, my Pretender kept casting Fear at the Berserk Lavas (morale 99). Does that do any good or is it a case of poor casting AI?