Spring Attack vs. Reach

[Macbrea]

Seriously... invisibility (100% cover),
-AK

Invisibility is 100% concealment and doesn't prevent AoOs.

 

[JESawyer]

Technically, you are correct, but I do not believe that a creature can take an AoO against a creature whom he or she is unaware of -- which makes sense.

 

[Tony Vargas]

You can only AoO an enemy you're threatening. If you suspect there may be an invisible character in the area, and you're swinging away wildly, hoping to hit it, and it does something to provoke an AoO, one of those wild swings has a chance to hit it... If you are unaware of the invisible character, the idea of taking an AoO against it makes less sense - it may be in your threatened area, but if you're making no attempt to hit it, are you really threatening /it/.

 

[Antikinesis]

Invisibility is 100% concealment and doesn't prevent AoOs.

Argh! You're right, it's concealment, not cover. Dunno what I was thinking.

-AK

 

[Vanye]

If you have a tower shield set at half cover you can do anything you want without provoking an AoO. The cover rules state it.

On the flipside, however, you can't make any AoO, either.