So my villain, under the effects of an invisibility spell, was forced due to irrelevant circumstances to attempt an overrun against one of the PCs. Obviously, the invisibility was ended by the overrun attempt, but then the question came up whether the PC should get an AoO against the villain.
Not being able to come up with a rule showing why he wouldn't, I allowed the attack, but was wondering if it had been stated anywhere if the invisibility would prevent an attack of opportunity. I know full concealment negates attacks of opportunity, but at what point does the concealment end in this situation - before or after the attack of opportunity would be provoked?
An AoO occurs before the provoking action takes place.
Invisibility ends when the wearer attacks.
Your villain provoked the AoO while still invisible, and so it was negated due to his/her full concealment.