That happened to me, although not quite so many. You can't use fire spells, but you can sure use others. I think I used Dehydrate a lot, and whirlwind.
Can you find a little nook where you can fight them a few at a time? One of the earliest spells my bishops acquire is Stamina, and later on Rest All. If you have either of those, that would help with the stamina problem, as would potions.
Failing all that, restore and try again.
