War Caster, a whip and a dagger, and provoking Opportunity Attacks

Question

This related question gives an answer about provoking opportunity attacks when wielding a dagger and a whip.

I am interested how this interacts with the feat War Caster (5e PHB p170):

When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making the opportunity attack.

The reason is that the reach property of the whip is only valid if the weapon itself is used for the opportunity attack.

Do I get an opportunity attack with a spell when a creature leaves a square

• adjacent from me (i.e. leaves dagger reach)?
• 5ft away from me (i.e. leaves whip reach)?

Please give an answer according to the RAW, and specifically mention either Mearls or Crawford's interpretation as basis, or answer for both.

Answer 1

The errata for the PHB includes this fix for reach weapons:

This property also determines your reach for opportunity attacks with a reach weapon.

So when a creature moves from 5 feet away to 10 feet away, you can make an opportunity attack with your dagger or cast a spell using War Caster. When a creature moves from 10 feet to 15, you can only make your opportunity attack with the whip.

Answer 2

Yes, you can cast a spell instead of an Opportunity Attack at either 5' or 10'

Let's look at the sequence of action and of the logic here:

1. Enemy is at in your current reach - They are currently in your active reach if you are wielding a whip because it has the Reach property which extends your reach when using it by 10' and they are also in range of your dagger if they are within 5'.

   This weapon adds 5 feet to your reach when you attack with it, as well as when determining your reach for opportunity attacks with it.

2. Enemy moves further away - This triggers an Opportunity Attack

   You can make an opportunity attack when a hostile creature that you can see moves out of your reach.

   The PHB Errata also confirms this:

   This property also determines your reach for opportunity attacks with a reach weapon.

   At this point, we know that when wielding a whip you have a 10' reach and that OAs are triggered when a creature leaves your reach. With your dagger, you have a 5' reach, and movement outside of that range triggers an OA with the dagger.

   The condition for leaving range has been met once they leave 5' for the dagger and after they leave 10' for the whip.

3. Cast a spell - War Caster lets you cast a spell instead of make an opportunity attack.

   When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity attack. The spell must have a casting time of 1 action and must target only that creature.

   This closes the loop on the action. We've covered that the OA is triggered at either 5' for the dagger or 10' because of your whip reach, and we've covered that when you get an OA with War Caster you can cast a spell instead. As long as the spellcasting requirements are met (range/components), then you can cast your spell in this case.

All conditions have been met (OA at 5' for the dagger and 10' from whip, cast spell instead of attack), so this works for both daggers and whips.

But there can be only one

Just a reminder that you only get 1 reaction per turn. If you use it at 5', then you've used it. If you wait until they leave 10', then you've used it then.

When you take a reaction, you can't take another one until the start of your next turn.

Answer 3

By RAW, yes to both.

When an enemy moves out of your reach, it provokes an opportunity attack from you, so when an enemy leaves the reach of your dagger or your whip it provokes an opportunity attack from you (rules on Combat):

You can make an opportunity attack when a hostile creature that you can see moves out of your reach.

The Reach property clarifies that such an opportunity attack can be provoked by a reach weapon based on that weapon's reach (rules on Equipment properties:

Reach. This weapon adds 5 feet to your reach when you attack with it, as well as when determining your reach for opportunity attacks with it.

If you are wielding both a dagger and a whip, the above means an enemy provokes an opportunity attack when it leaves the reach of either weapon, which will occur if an enemy moves from 5 feet to 10 feet away or from 10 feet to 15 feet away. Note that the wording of the Reach property clarifies that your extended reach for your whip does not somehow extend your reach for the dagger. Your opportunity attacks with the whip have reach but your opportunity attacks with the dagger are still adjacent only. This won't be relevant to our scenario, for a reason you will see below.

If you have the War Caster feat, when an enemy provokes an opportunity attack from you due to movement, you can forego the opportunity attack and instead use your reaction to cast an eligible spell (rules on War Caster):

When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity attack.

There are two very significant rules our scenario hinges on:

1. By RAW, the only requirement to trigger the War Caster option is that a hostile creature provokes an opportunity attack with its movement. There's no rule that you have to actually make or be willing to make or be in the process of making said opportunity attack with a certain weapon; in fact, you're specifically skipping that opportunity attack. There's also no restriction on the nature of how that movement provoked an opportunity attack, only that it did.

2. By RAW, when you use the War Caster option, you're not getting an opportunity attack with the spell. You are skipping the opportunity attack and instead using your reaction to take the special spellcasting option afforded to you by the feat. So the question is not whether you "get an opportunity attack with a spell" but whether you "get to cast a spell in lieu of an opportunity attack."

Then we have enough to solve each of the cases in our scenario.

• Can you apply War Caster when a creature leaves the reach of your dagger (moves further away than 5 feet)? It provoked an opportunity attack from you by movement, right? Then yes, cast that spell.

• Can you apply War Caster when a creature leaves the reach of your whip (moves further away than 10 feet)? It provoked an opportunity attack from you by movement, right? Then yes, cast that spell.

In summary, War Caster's trigger and thus its applicability is the same for the dagger and the whip (except for the distance at which it triggers): when an enemy provokes an opportunity attack by moving. There's no difference between the weapons with respect to this trigger.

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This RAW answer does not rely on or consider any designer clarifications, since those aren't RAW. It does account for the current version of the text (meaning the errata available as of this post).

Answer 4

War Caster feat:

When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making the opportunity attack.

As long as the OA is triggered by a hostile enemy's movement you can cast a spell with your reaction instead. This is confirmed by Jeremy Crawford's ruling here.

Thus in your example in the question, a spell casting creature with the War Caster feat a whip and a dagger can cast a spell at someone moving and leaving their 10' reach with the whip, and their 5' reach with the dagger.

Answer 5

The answer is the same as the related question.

If your preferred answer to the related question is, "you get an opportunity attack", then you can replace that attack with a spell instead. If your answer is, "you don't get an opportunity attack", then there is no opportunity attack to replace, and thus you can't cast a spell.