Attacks of Opportunity

[bwhetherington]

Attack of Opportunity should be a standardized term, rather than simply applying to when a creature moves out of the reach of your weapon. It's already used in a few cases, such as those and Polearm Master. I propose that we try to further standardize and clean up language relating to attacks of opportunity.

Cases that come to my mind in particular are Polearm Master (which Mike Merles has stated requires that the AoO be made with the triggering weapon), and Mage Slayer, which has very similar language to AoO, but does not specifically call the attack you make one of opportunity. Berserker's Retaliation could also be considered an AoO.

[JamesMcClung]

I think "opportunity attack" is already a standardized term (PH 195), it's just not common for things to grant new means of making one.

Making Retaliation and Mage Slayer grant opportunity attacks would not be without consequence. Any enhancements to opportunity attacks (such as that of Sentinel or the Blade Mastery UA feat) would apply to them. And though there aren't many ways to enhance OAs currently, future enhancements to OAs becomes more difficult when one must consider more than just the base case of "a creature left your reach without disengaging". Even Sentinel alone is a bit of a pain in this regard.

Not everything that grants a MWA as a reaction should be an opportunity attack flavorwise, either. The name "opportunity attack" implies taking advantage of an opponent's bad decision. Mage Slayer sort of has that flavor—maybe the mage slayer trained to identify when a spellcaster is most vulnerable—but Retaliation as a Berserker feature is harder to justify.

Lastly, consider Sentinel, which enhances OAs, gives a new OA trigger, and gives a new MWA trigger. It's clear that that MWA is not supposed to be an opportunity attack. I think it's likely that all other MWAs are deliberately not opportunity attacks.

The decision to convert something to an OA should be based on both fluff and mechanical interactions. Even if some MWAs are converted to OAs, some will not be, so any cleanup attempt will be incomplete.