With this spell, you cause the target creature to instantly believe that a cloud of fog has suddenly enveloped her. The effect obscures all sight, including darkvision, beyond 5 feet. A creature within 5 feet has concealment (attacks have a 20% miss chance). Creatures farther away have total concealment (50% miss chance, and the target can't use sight to locate the creature). The target does not make an initial disbelief save if it has ever encountered or has knowledge of the fog cloud spell (ranks in Knowledge (arcana) or Spellcraft).