War Caster 5e Guide

War Caster 5e Guide: Everything You Need to Know

There’s only one monster left on the battlefield. The ogre looks around and, not wanting the same fate, begins to run away. The fighter who was facing the ogre doesn’t let that happen. She raises her maul above her head and makes an opportunity attack against the ogre as it flees. However, this opportunity attack is not a normal one. With her maul glowing, she casts a spell, and the ogre is destroyed by thunderous energy.

Which ability allowed the fighter to achieve such power? How was she able to cast a spell as an opportunity attack? How can you be as cool as her? The answer lies in the War Caster feat.

What is the War Caster Feat?

War caster

The War Caster feat is one of the many feats found in the Player’s Handbook in D&D 5e. Feats are optional abilities that player characters can access when they reach certain levels. Whenever you reach a level that grants an ability score improvement, you can forgo the ASI and take a feat instead.

While feats are technically an optional rule, they are widely accepted at D&D tables. It is still worth checking with your DM whether or not they allow feats in their game. 

If you take the War Caster feat, you receive the following benefits:

  • You have an advantage on Constitution saving throws to maintain concentration on a spell when you take damage.
  • You can perform the somatic components of spells even when you have your hands full.
  • You can cast a cantrip as an opportunity attack rather than make a melee attack.

This feat also has a prerequisite: you can only take this feat if you have the ability to cast at least one spell.

Let’s continue our war caster 5e guide and break down what each of these features means.

Constitution Saving Throws to Maintain Concentration

Many of the most powerful spells that last longer than one turn require your concentration. This means that you are actively focused on maintaining the spell’s effects. If you lose concentration, the spell can end early.

The most common way of losing concentration on a spell is by taking damage. When you take damage, you must make a Constitution saving throw with a DC equal to either 10 or half the damage you took (whichever is higher). If you fail, the spell ends.

This feat, therefore, increases your chances of maintaining concentration on a spell by granting you the advantage on the saving throw.

Somatic Components With Your Hands Full

Whenever you cast a spell in D&D, you must be able to fulfill the required components to cast the spell. A verbal component means you must be able to speak. A somatic component means that you must have a hand free to wave around. Material components are physical items that you must have on your person to cast the spell.

This feat allows you to perform the somatic components of the spell without needing a free hand. While this feat does not have a direct effect on the material components of spells, there are indirect consequences. This is because the PHB states that “a spellcaster must have a hand free to access a spell’s material components—or to hold a spellcasting focus—but it can be the same hand that he or she uses to perform somatic components.”

Component Pouch

If you use a component pouch, you still need a hand free to access your pouch for spells that require material components.

Musical Instrument or Arcane/Druidic Focus

Musical Instrument

If you use a focus, you need to be holding the focus in order to cast spells with material components.

Holy Symbol

If you have a holy symbol as your spellcasting focus, things get complicated with regard to spells that require somatic and/or material components. For our purposes here, we will assume that any verbal component can be performed. There are three possible requirements to cast a spell.

Without the War Caster feat:

  • Somatic only. You need a hand free to perform the somatic components.
  • Material only. The hand that holds your shield emblazoned with your holy symbol fulfills this requirement.
  • Somatic and Material. The hand that holds your shield fulfills the material component. Since you can use the same hand that holds your spellcasting focus to perform the somatic component, you can cast this spell.

With the War Caster feat:

  • Somatic only. The feat allows you to perform somatic components without having a hand free.
  • Material only. Same as above.
  • Somatic and Material. Same as above.

Material Components with a Gold Cost

Regardless of what you use as your spellcasting focus, if a spell requires a material component that has a gold cost specified in the spell, you must have a hand free to access the specific components. This is the case whether or not the material components are consumed.

Cantrips as Opportunity Attacks

Cantrip 5e

When a creature leaves your reach in D&D, you are able to use your reaction to take an opportunity to attack against them. Normally, this attack is a melee attack using whatever you have in your hand. 

If the weapon you are holding is a simple weapon or if you don’t have anything in hand, you won’t be able to do much with your opportunity attack. However, this feat allows you to cast a cantrip instead when someone runs away from you. Since cantrips scale in damage as you level up, this can be a particularly large difference and for many classes, making an opportunity attack becomes a reliable source of damage.

War Caster vs Resilient Constitution

Many players read this feat and are only interested in one or two of its three abilities. If you are considering taking this feat solely for the advantage on Constitution saving throws, consider taking the Resilient feat instead.

The Resilient feat allows you to boost an ability score by one and gain proficiency in saving throws using that chosen ability. If you choose Constitution, you will gain proficiency with all Constitution saving throws.

Which is better? Taking Resilient Constitution at 1st or 4th level will give you a bonus of +2. This bonus is a +3 if your Constitution modifier is boosted. War Caster gives you the advantage on your Constitution saving throws. Advantage is not a static bonus, but it improves the probability of rolling a higher number.

Rolling with advantage gives you an average of a +3 boost to your roll. However, this varies as you increase the DC of the check. When you roll to maintain concentration checks, you often only need to roll an 8 or higher (assuming a Constitution modifier of +2). Rolling with advantage boosts your chance of meeting this by almost 25% or +5.

As you level up, your proficiency bonus increases as well, to a maximum of +6. This means that at higher levels, your bonus to your Constitution saving throws will reach a +8 (again assuming a Constitution modifier of +2).

At lower levels, the advantage on Constitution saving throws is better, but proficiency will soon overtake it. If you don’t expect to play this character at higher levels, you may decide to take the War Caster feat. Of course, if you are an artificer, Eldritch Knight, or a sorcerer, you will already be proficient in Constitution saving throws, and you won’t have to make this choice.

Which Classes Should Take War Caster?

After breaking down the benefits of the feat, which classes or subclasses will benefit the most from it? Let’s take a look.



Artificers already have proficiency in Constitution saving throws, so you won’t have to decide whether to take Resilient or War Caster for the concentration bonus. Moreover, artificers that spend time in melee—like the Battle Smith— won’t need to worry about stowing and drawing their weapons in order to cast spells. 


Many bard spells require concentration, and martial bards such as the College of Valor or the College of Swords can use the other abilities. College of Swords bards use their blade as their spellcasting focus, solving the issue of material and somatic components.

Bards only have access to Vicious Mockery as a cantrip that deals damage, which can still be a decent option as an opportunity attack as you hurl an insult at someone running away from you.



Clerics already circumvent the normal problems with somatic components by emblazoning their holy symbol on their shield. This feat lets you also solve the issue of casting spells with somatic components but without material components.

Some clerics also gain Potent Spellcasting, which makes their cantrips significantly more powerful than attacking with a mace, making this feat a great choice.


The concentration boost is good for all druids, but you will rarely be unable to perform the somatic components of your spells. Opportunity attacks differ between the subclasses. Circle of the Moon druids will not be casting cantrips as opportunity checks as they will spend most encounters in their Wild Shape form, while other druid circles tend to stay in the backline of combat. 

Therefore, you should not be making many opportunity attacks anyway. Maintaining concentration on spells can be incredibly useful for many druids, especially Circle of the Shepherd druids, who rely on concentrating on their summoning spells. 

Eldritch Knights

Eldritch Knights

This feat is perfect for Eldritch Knights. Fighters already have proficiency in Constitution saving throws. Gaining advantage as well makes your concentration checks very strong. Many of your best spells require somatic components but not material components.

With this feat, you can carry a sword and shield or a heavy, two-handed weapon and still cast spells. Lastly, most Eldritch Knights cast Booming Blade instead of taking the attack action. Being able to cast this cantrip as an opportunity attack will trigger additional damage if they continue to run away.

Unfortunately, you won’t be able to pick this feat up at level 1 since it has a prerequisite of being able to cast one spell. Both the Variant Human and Custom Lineage do not enable you to do this, so you will have to wait until the 4th level.


Paladins operate much like martially focused clerics, being able to wade into battle with your holy symbol emblazoned on your shield. The advantage of concentration is useful if you want to cast Heroism or Shield of Faith, but it’s not necessary.

Your opportunity attacks as a paladin will primarily be with your weapon, and most paladins don’t learn cantrips, making that feature of War Caster useless unless you access cantrips in other ways. Similar to the Eldritch Knight, you will not be able to pick this feat up at 1st level since you only get spellcasting at 2nd level.



As a ranger, maintaining concentration on your few spells can be very useful. You will rarely be unable to perform the somatic components of spells, and you typically won’t learn any cantrips unless you take Druidic Warrior.

You also won’t be able to take this feat at 1st level through Variant Human or Custom Lineage since you gain spellcasting at 2nd level.

Arcane Tricksters

Arcane Trickers are similar to Eldritch Knights in that they are a spellcasting subclass of a martial class. However, this subclass is focused on illusory and enchanting magic instead of the evocation of an Eldritch Knight.

Nevertheless, War Caster for an Arcane Trickster can be a powerful combination. The biggest benefit is being able to cast Booming Blade as a reaction and trigger its additional damage and your sneak attack damage. Your sneak attack works once per turn, not per round, so if you have the advantage of if there’s an ally within 5 feet, you can deal an absurd amount of damage.



Sorcerers are the only arcane class with proficiency in Constitution saving throws. Gaining advantage as well makes your concentration checks reliable at all levels. You won’t typically worry about performing somatic components.

Casting a cantrip instead of making a melee attack will be much more powerful. However, you have a d6 hit die. You won’t want to be so deep into combat that you’re making opportunity attacks against anyone, and if someone is running away from you, you should be thankful.


The boost to concentration is especially nice when you have such few spell slots. However, the biggest benefit of this feat comes to Hexblade and Pact of the Blade warlocks. Warlocks are an arcane class, but the Hexblade turns it into a melee combatant. You’ll need the boost to concentration, and you won’t want to put your weapon away to cast spells.

If you plan to cast eldritch blast as your opportunity attack, you will be able to fire the normal amount of beams according to your level as long as they all target the creature provoking the opportunity attack. Unfortunately, these attacks will all be made at a disadvantage since the eldritch blast is a ranged attack, and the creature is within 5 feet when you make the opportunity attack. 



Like all spellcasters, maintaining concentration on spells is incredibly useful. However, that’s the biggest benefit of this feat for wizards. You won’t be juggling many weapons to be unable to perform somatic components, and you won’t want to be close enough to anything to take an opportunity attack.

The exception to all of this is the Bladesinger. Bladesingers in melee will want to maintain concentration on their spells. You will most likely have a hand free to perform your somatic components. Lastly, being able to cast Booming Blade as an opportunity attack is just as powerful for the wizard as it is for the Eldritch Knight.


Question: How good is the war caster feat?

Answer: A war caster feat is a powerful option for “gish” characters: good with both martial and spellcasting. This includes the Battle Smith, Eldritch Knight, Arcane Trickster, and Hexblade warlock.

Question: Is War Caster better than resilient?

Answer: Technically, Resilient Constitution is better than War Caster for maintaining concentration. However, War Caster is better at lower levels while your proficiency bonus is lower and still very effective at rolling at least a 10, which is what you need most of the time.

Question: Can you cast a cantrip with War Caster?

Answer: Yes, one of War Caster’s three benefits is being able to cast a cantrip as an opportunity attack.

Question: Can you cast Magic Missile with War Caster?

Answer: No. Magic Missile is a 1st level spell. War Caster only allows you to cast a cantrip as your reaction.

Question: Can you cast Eldritch Blast with War Caster?

Answer: Yes, but every beam must target the creature that provoked the attack, and each attack roll is made with a disadvantage because it is a ranged attack, and there is a hostile creature within 5 feet of you.

War Caster 5e Guide: Summary

War Caster is a feat available to any character who can cast at least one spell. It has three main benefits:

  • You have an advantage on concentration checks.
  • You can perform the somatic components of a spell with your hands full.
  • You can cast a cantrip as an opportunity attack.

In order to get the most out of this feat, you want to be able to benefit from all three of these features. This feat is most powerful for the Eldritch Knight, Hexblade warlock, and Battle Smith.

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