I was surprised to find no mention of this in the Opportunity Attack rules on d20pfsrd or on the Paizo SRD: if an enemy moves from tile A to tile B and provokes an opportunity attack from me in doing so, are they in tile A or B when I perform the opportunity attack?
This is a minor detail, but pretty significant!
- I'm a mundane human with a sword and threaten squares adjacent to me. If my enemy starts their turn adjacent to me then walks away out of range, do I make an opportunity attack as if they're still in range, or do I lose it because they're too far away?
- I have a spear with a reach of 10 feet, and I can't attack foes in adjacent squares with it. An enemy walks up to me, through my threatened range of 10 feet. When they leave my threatened tile to step up adjacent to me, do I take an opportunity attack as if they're 10 feet away, or do I lose it because they're too close?
- Let's say I'm Gargantuan, and an enemy wants to walk through my range. When they take the movement which provokes an opportunity attack from me, where are they when I make my opportunity attack? (Pretend it's very important: I have an ability that will cast in a straight line and might hit multiple targets or none at all, or I might inadvertently smash a pressure plate, etc)
In all cases, ignore 5-foot steps and pretend my enemy has walked far enough to provoke an opportunity attack.