Face in the Crowd (Sp)
At 1st level as a standard action, you can cause yourself to appear so normal, mundane, and unexceptional that you blend in to your surroundings. All creatures within 30 feet treat you as if you belonged there, effectively ignoring you. Creatures outside of this area may notice that you appear out of place, but as soon as they approach within 30 feet they are affected by the magic and no longer think something is amiss. If you interact with an affected creature in any way, it gains a Will save (DC 10 + 1/2 your wizard level + your Intelligence modifier) to disbelieve the illusion and notice you. The effect lasts for a number of minutes equal to your wizard level, or until the illusion is dispelled. The minutes do not need to be consecutive, but must be used in 1-minute increments. This is a mind-affecting phantasm effect.
This ability does not turn you invisible and opponents are not considered flat-footed. It does not allow you to disguise yourself as a specific individual, type of person, or member of another race, so you cannot blend into a group of uniformed guards or appear as a member of an individual’s family, and a human cannot blend into a group of gnolls. You can blend in with any group made up of different types of people, such as a crowd of courtiers in a king’s throne room, and you can disguise yourself (either through magic or more mundane means) to appear as a specific type of person or another race (such as a uniformed guard or a gnoll) before using this ability.
Can you use this ability once you have already been the target of a spell or attack to remove your self from combat as a target and move around unhindered ?
In a crowd of similar looking creatures (bunch of humans for a human) I think you could, but having been a target of a spell, it is fair to say you have been interacted with, allowing the will save. But if conditions are not "a face in a crowd", i.e. there is no crowd, no way.
If an opponent knows you have this ability, a detect magic could go a long way in rediscovering you. This is sort of Hide-In-Plain-Sight for crowds.