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 doesnt protect a creature from spells
for which SR doesnt 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.