[Jarkko]

Quagmire + Rain + Androphag Archers.

All sorts of snares (you have access to a ton of cheap N mages to cast tangle vines) are your friends.

Send in waves of imps, they are immune to the heat, and they will delay the heavy Abysian infantry (and the heavy infantry will get more and more exhausted).

If you can, summon some earth elementals for the battle. They'll trample the Abysian infantry. Yeah, the elementals will faint from exhaustion too, but they will still take some beating even when unconcious, during which time your Androphag Archers keep on peppering.

Ie anything that will make your androphag archers shoot for as long as possible is good for you.