The warded creature is immune to the effects of one specified spell for every four levels the character has . The spells must be of 4th level or lower. The warded creature effectively has unbeatable SR regarding the specified spell or spells. Naturally, that spell immunity doesn’t protect a creature from spells for which SR doesn’t apply. Spell immunity protects against spells, spell-like effects of magic items, and innate spell-like abilities of creatures. It does not protect against supernatural or extraordinary abilities, such as breath weapons or gaze attacks. Only a particular spell can be protected against, not a certain domain or school of spells or a group of spells that are similar in effect.
A creature can have only one spell immunity spell in effect on it at a time.