darkness, darkness spell, concealment, total concealment, and attacks of opportunity

[bjoern]

Had a situation last night where we were trying to figure out if someone who has concealment (20% miss chance) provokes attacks of oopportunity by leaving a threatened square. The attacker would still have to "guess" which square to attack and then have his miss chance on top of that.

Players handbook says that AoO cannot be made against someone with total concealment (50% miss chance) but makes no mention about 20% concealment that we could find.

Also, natural darkness gives total conealment, 50% miss chance and thus immunity to AoO.
But the darkness spell gives only 20% concealment and therefor allows AoOs.

Are we missing something...?

[Flickerdart]

Regular concealment is insufficient to hide the creature's square from the attacker. The darkness spell does not create true, natural darkness, but only shadowy illumination (regular concealment). In an area of natural darkness, a darkness spell actually makes it easier to see.

[bjoern]

So, in magical darkness, are AoOs provoked from movement through threatened squares?
Does an attacker have to guess which square to hit?

[WhamBamSam]

So, in magical darkness, are AoOs provoked from movement through threatened squares?
Does an attacker have to guess which square to hit?You can absolutely AoO (with the 20% miss chance) in magical darkness or against things with partial concealment. You also know which square the creature you're AoOing is in.

In cases where the creature has total concealment, I don't think you can AoO them even if you do know the exact square they're in through something like Blindsense. The "guessing the square" thing applies more to stuff you do on your own turn.

Being able to pinpoint a creature's location is sort of a separate issue from how much concealment the thing has. This is pretty much exactly the difference between Blindsense and Blindsight.