recommended fire protection items?

[Evil Dave]

At the high end for battle spells there's also Army of Gold (Alt9, E4) and Gaia's Blessing (Ench 9, N6E2) both of which 50% FR to all your troops. Gaia's blessing gives 50% resistance to the other elements, too.

[Lingchih]

But 50% only brings a Jarl up to 0, since they are already susceptible to fire. You need a helmet and fire plate, or a helmet and burning pearl, or all three.

It's very tough to make Jarls resistant to the nasty end game fire spells. You pretty much have to have killed off your fire wielding opponent by then.

If you can empower a Jarl (or some other commander) up to F2, they can cast Fire Fend, which covers several spaces (5, I think), and works quite nicely.

[ComTrav]

Rain, easily accessible, increases the fatigue from casting fire spells. W2E2 lets you cast Fire Ward.

[Szumo]

If you want to wish, wish for one of the elemental fire kings, then you'll have plenty access to fire