When this spell is placed upon a creature by a priest, the creature's body is toughened to withstand heat or cold, as chosen by the caster. The spell grants the creature complete immunity to mild conditions (standing naked in the snow or reaching into an ordinary fire to pluck out a note). The recipient can somewhat resist intense heat or cold (whether natural or magical in origin), such as red-hot charcoal, a large amount of burning oil, flaming swords, fire storms, fireballs, meteor swarms, red dragon's breath, frostbrand swords, ice storms, wands of frost, or white dragon's breath. In all of these cases, the temperature affects the creature to some extent. The recipient of the spell gains a bonus of +3 to saving throws against such attack forms and all damage sustained is reduced by 50%; therefore, if the saving throw is failed, the creature sustains one-half damage, and if the saving throw is successful, the creature sustains only one-quarter damage. Resistance to fire lasts for one round for each experience level of the priest placing the spell.
The caster needs a drop of mercury as the material component of this spell.