The caster could protect one creature from one type of damage (either natural or magical in nature) per casting of this spell. All clothing and equipment worn or carried by the recipient were also protected. Higher level casters could double or even triple the damage absorption afforded by this spell. If the protected creature was exposed to damage from the chosen energy type, a modest amount was absorbed for each separate exposure while the spell remained in effect. Any damage over the absorption limit was felt by the recipient.
Note that this spell did not grant immunity from secondary effects, such as the lack of oxygen if immersed in acid or encased in ice.
Resist energy was a lesser form of protection from energy and the two spells did not stack. That is, if both spells were cast on the same creature with the same chosen energy type, the greater protection from energy would operate until discharged and only then would resist energy begin to work.