This spell causes the creature touched to vanish from sight and be
undetectable by normal vision or even infravision. Of course, the invisible creature is
not magically silenced, and certain other conditions can render the creature
detectable. Even allies cannot see the invisible creature or his gear, unless these
allies can normally see invisible things or employ magic to do so. Items
dropped or put down by the invisible creature become visible; items picked up
disappear if tucked into the clothing or pouches worn by the creature. Note, however,
that light never becomes invisible, although a source of light can become so
(thus, the effect is that of a light with no visible source).

The spell remains in effect until it is magically broken or dispelled, until
the wizard or recipient cancels it, until the recipient attacks any creature, or
until 24 hours have passed. Thus, the invisible being can open doors, talk,
eat, climb stairs, etc., but if he attacks, he immediately becomes visible,
although the invisibility enables him to attack first. Note that the priest spells bless, chant, and prayer are not attacks for this purpose. All highly Intelligent (Intelligence 13 or
more) creatures with 10 or more Hit Dice or levels of experience have a chance
to detect invisible objects (they roll saving throws vs. spell; success means
they noticed the invisible object).

The material components of the invisibility spell are an eyelash and a bit of gum arabic, the former encased in the
latter.