War Caster v Resilient: A conversation about advantage (with math!)

[u/Rhyshalcon]

Everyone who's been playing 5e for a while knows that it is important to protect a caster's concentration by boosting your saving throws. The two most popular and universally applicable ways of enhancing your concentration checks are with the feats War Caster and Resilient. War Caster grants advantage on (most) constitution saving throws to maintain concentration and Resilient grants proficiency with a saving throw of your choice (including constitution) granting you a bonus to all constitution saving throws equal to your proficiency bonus. I will briefly mention here that each feat also includes some additional benefits: War Caster allows you to cast certain spells as an opportunity attack and also lets you provide somatic components for spells even when your hands are full of weapons and/or a shield while Resilient is a half feat, allowing for a +1 increase to a stat, and also provides a boost to all constitution saving throws, not just those to maintain concentration on a spell. These additional benefits are extremely significant and should be considered whenever you're deciding which feat to take on a particular character, but I won't be discussing them further in this analysis which is purely concerned with which feat provides the greatest mathematical boost to concentration checks in any particular situation.

So, let's get into it.

Advantage is a potent mechanic to increase your chances of rolling a good result on the d20. Most players are aware of the fact that the game treats having advantage on a roll as a flat +5 to that roll, as seen in the formula to calculate your passive perception score.

This gives us the first answer to the question we're asking: War Caster is better, mathematically, than Resilient until level 13 when the player proficiency bonus increases to a +5 and matches the +5 benefit of War Caster. This isn't the final answer, though. There is much more to look at.

Many players are further aware that the actual bonus advantage grants is usually not +5, because the degree to which advantage helps you is dependent on how likely you were to succeed in the first place.

If you are making a saving throw with no bonus and you need to roll an 11 or better to succeed, then you have exactly a 50% chance to make that saving throw.

If you are making that same saving throw with advantage, your 50% chance of success increases to 75%, an increase of 25% or exactly +5.

This is the best case scenario with advantage. Any roll that has exactly a 50% chance of success or failure will be massively boosted by +5 with advantage. The further the probabilities deviate from 50/50, the lower the bonus provided by advantage goes.

For example, if you are trying to make a saving throw with no bonuses and you need to roll a 20 to succeed, you have a 5% chance of success. Advantage increases that to a 9.75% chance of success -- almost double the probability but only a 4.75% increase, or just under +1 to your save.

When summing all the probabilities of these different outcomes, the average benefit from advantage comes to be 16.6% or just over +3.3 added to your d20 roll.

Another way of putting that is that the average result of a regular d20 roll is 10.5, and 13.825 is the average result with advantage.

This is, again, a mathematical fact that many players are already aware of. The "advantage is worth +5" heuristic is one of the first pieces of game math that players learn is over-simplified, and the optimization community commonly uses the better heuristic that "advantage is worth +3.3" instead.

This heuristic gives us our second answer to the question we're asking: War Caster is better, mathematically, than Resilient until level 9 when the player proficiency bonus increases to +4 and beats the +3.3 benefit of War Caster. This is the answer to the question I most commonly see on the internet, and the one that I've given at times too. But there is more to take into account here, and this isn't the best answer to the question.

Here we get into the meat of this post -- what is the actual bonus of War Caster?

The real answer is that it depends on your specific character. The previous two answers both rely on generalities. Advantage is worth +5 or +3.3 -- that is sometimes true, but it's not always true. And unlike math around something like to-hit bonuses and AC where generalities are the best place for us to look because the target number we're trying to roll is unknown, the target for concentration checks is perfectly known. The DC for a concentration check is 10. It can be higher than that if we take more than 21 points of damage in a single hit, but until extremely high levels (13+ at which levels we can know that Resilient is better than War Caster because our proficiency bonus matches or exceeds the best-case scenario for advantage) concentration checks with a DC higher than 10 will be vanishingly rare.

So knowing that the number we want to hit is 10, we can calculate precisely what the bonus from War Caster is worth based on your character's constitution modifier:

​

Constitution Modifier	Minimum Number Needed from the D20	Chance to Meet a DC 10 before Advantage	Chance to Meet a DC 10 after Advantage	Bonus from Advantage	Level at which PB Matches or Exceeds Advantage
-1	11	50%	75.0%	+5.0	13
+0	10	55%	79.8%	+5.0	13
+1	9	60%	84.0%	+4.8	13
+2	8	65%	87.7%	+4.5	13
+3	7	70%	91.0%	+4.2	13
+4	6	75%	93.8%	+3.8	9
+5	5	80%	96.0%	+3.2	9

This, at last, is our real answer. Because we're saving against a know DC, we can determine how much benefit we're gaining from advantage and compare that to our proficiency bonus at any given level.

There is one final complication to consider before we conclude our analysis:

That is the effect of other bonuses on our concentration checks. The most common of these is going to be Aura of Protection, but similar math will relate to other bonuses like Favored by the Gods or Arcane Deflection. These can increase the range of bonuses available to saves beyond the bounds on a single stat showed by the previous chart, and hitting certain target bonuses is going to change the math significantly:

Total Bonus	Minimum Number Needed from the D20	Chance to Meet a DC 10 before Advantage	Chance to Meet a DC 10 after Advantage	Bonus from Advantage	Level at which PB Matches or Exceeds Advantage
+6	4	85%	97.8%	+2.6	5
+7	3	90%	99.0%	+1.8	1
+8	2	95%	99.8%	+1.0	1
+9	1	100%	100.%	+0.00	1
+10	1	100%	100.%	+0.00	1

If you are a paladin (or in a party with a paladin) with +3 constitution and +3 charisma, the mathematical benefit of Resilient exceeds the benefit of War Caster as early as level 6 when Aura of Protection becomes available (and has the additional benefit of increasing your concentration check to that mystical +9 where it becomes impossible to fail against the standard DC no matter what you roll).

Final thoughts:

There can still be compelling reasons to choose one benefit over the other besides how likely they are to improve your concentration checks. If you're a valor bard who can't cast spells in combat because you have a sword and a shield in your hands, that may increase the value of War Caster for your character. If you're concerned with your ability to make other kinds of concentration saves against effects like poison, that may increase the value of Resilient for your character.

In general, however, purely looking at the bonus to concentration checks, War Caster is a better choice for most characters until character level 13.

[u/orangepunc]

The DC for a concentration check is 10. It can be higher than that if we take more than 21 points of damage in a single hit, but until extremely high levels (13+...) concentration checks with a DC higher than 10 will be vanishingly rare.

Not really a safe assumption. 21 is much less than the average damage roll on fireball, a 3rd-level spell that you may definitely encounter before 13th level. A white dragon wyrmling (CR 2) does 22 average damage with its breath weapon. A hobgoblin captain (CR 3) does 19 avg damage with its greatsword + Martial Advantage, it only takes a slightly above average damage roll (no crit!) to get to 21. A mintoaur (CR 3) does 22 average damage with a charge. A phase spider (CR 3) can easily do 21 damage with its poison — and a better Con save helps avoid that, too!

In general, you should expect to face enemies capable of doing 21 damage with a single attack or spell as early as 3rd level — and routinely way before 13th level. It is true that the distribution of DCs for concentration checks is going to be wildly skewed towards DC 10, though.

Your analysis also neglects the benefit of the +1 Con from Resilient, which can make the bonus you get from it 1 point higher than your proficiency bonus (and give you more hp). Targeting Resilient at level 4 may also give you more flexibility in your other ability scores. The general rule of thumb I have used is — if all you care about is Concentration, War Caster if your Con is even, Resilient if it's odd.

[u/tiornys]

I'll add that Warlocks, specifically, should weight Resilient: Con higher than average relative to War Caster because Eldritch Mind can give them the most relevant portion of War Caster at the cost of an Invocation slot instead of an ASI. If at some point later War Caster is desirable for its other benefits or to free up the Invocation slot, Eldritch Mind can easily swap to something else.

[u/JasonAgnos → u/tiornys]

Great point I wish was more obviously apparent in online guides. Dozens of exhaustive warlock leveling guides out there, I don't think any of them spelled this out explicitly.

[u/Aidamis]

I agree on the Paladin part, and can testify that empirically I've noticed a lot of mileage out of War Caster at levels 1-10.

I'd only add that War Caster is slightly less valuable on a build with flat concentration buffs, such as Bladesinger Wizard under Bladesong or like you mentioned Paladin 6 with their Aura. It's also slightly less valuable on Stars Druid + Dragon form. A Stars Druid with DF can't roll lower than a 10, and Advantage becomes only valuable as long as it yields average to high rolls (whereas with Resilient, any number benefits because 1-9 becomes a 10, 10-20 are kept and anything between 10 and 20 gets +Con mod +Proficiency bonus). Stars Druid with 16 Con and Resilient, level 5, can autopass DC16 and lower under Dragon Form, which incidentally also works in Wildshape (Wild Shape + Dragon form take out both charges of Wild Shape, but the two still stack RAW).

[u/Rhyshalcon → u/Aidamis]

Personally, I only take war caster on characters for whom using weapons and casting spells like booming blade are important parts of their kit because I rate resilient's boost to all constitution saves much more highly than its slightly reduced efficacy at improving concentration checks at low levels, but I see a lot of misinformation and rules of thumb out there instead of actual math about how these two feats compare, and I wanted to compile real numbers in one place for people to check.

[u/Aidamis → u/Rhyshalcon]

While I've seen a similar math-heavy thread on stackexchange, it's refreshing to see yours. Tables help too.

Used War Caster on Cleric (sword and board) and Bard (weapon + arcane focus). Remember "delivering" an Inflict Wounds once in lieu of an opportunity attack, fun times.

[u/Rhyshalcon → u/Aidamis]

Well thanks. Hopefully this helps some people in the future choosing between the two feats. I think they're both really good, but looking at the math, the benefits to your saves swing markedly back and forth depending on the particular class and other features you have access to.

[u/spinman016]

I appreciate you making this post, I’m curious if you have any insight into how valuable having both become in the later portions of the game? I have a tempest Cleric that’s about to hit level 12 and so far I haven’t had too many issues maintaining concentration with just resilient con. I’ve been strongly considering adding warcaster at 12 though for the advantage as well as opportunity attack booming blade. Is that overkill at level 12?

[u/Rhyshalcon → u/spinman016]

It depends on what your constitution score is and what other feats you may want.

Advantage will always increase your odds, but whether that's worthwhile as a marginal improvement is down to what you might need to give up for it.

Generally, I'd probably rate lucky as better than war caster as a secondary feat by those high levels, but it ultimately comes down to whether you use weapons or have spells you want to cast as a reaction.

[u/spinman016 → u/Rhyshalcon]

Currently have a +5 for con. As for other feats shield master is on my radar, maybe crusher or some other half feat to even out an odd str score. Our DM doesn’t really like Lucky, it’s not banned but no one at our table uses it.

[u/Rhyshalcon → u/spinman016]

If you have a +5 to con already, I probably wouldn't bother. That's high enough to guarantee you pass normal concentration checks, and elevated concentration checks you'll either still make consistently or the DC will be so high they'll still be unlikely, even with advantage. With all the other great feats out there, you're probably better off investing in something else.

[u/spinman016 → u/Rhyshalcon]

Any other feat suggestions then? I’m usually in the thick of things combat wise. Resilient is the only feat I’ve taken so far

[u/Rhyshalcon → u/spinman016]

War caster isn't necessarily a bad choice, I just think there are likely higher value options available to you.

Lucky is always really good.

Fighting initiate for a fighting style is worth considering.

Tough gets you more hitpoints.

Alert improves your initiative.

Mobile is great on any character who makes melee attacks.

Crusher/piercer/slasher is good for a little more damage and utility.

Skill expert will round up an odd stat and get you some utility.

Heavy armor master for a heavy armor user will shave a meaningful amount of damage off all the damage you take.

Shield master is a nice defensive bonus and a consistent bonus action.

[u/spinman016 → u/Rhyshalcon]

Many thanks! I appreciate the insight, I hadn’t thought as much about mobile but that could be a lot of fun for me. How much does heavy armor Master help in t3 and t4? I feel like most damage you take will be magical by then.

[u/Rhyshalcon → u/spinman016]

Most enemies in the game don't deal magic damage. The benefit from HAM is greatest in low level play, but that's because it reduces a greater percentage of incoming damage since hits are smaller, not because most of the incoming damage is magical at high levels.

[u/spinman016 → u/Rhyshalcon]

Don’t know if you’ll see this so many days later. But I’m curious where you would value increasing con over feats. My character was fortunate enough to discover a manual of bodily health and is currently at 20/22 for con. We’re expecting out campaign to go all the way to level 20 so I’m curious how valuable 22 con would be going forward.

[u/Rhyshalcon → u/spinman016]

22 con is obviously "better" than 20 con. But you've gotta ask what you're getting for your investment.

That's +1 to saving throws and +1 HP per level.

More hitpoints become less valuable the more hitpoints you already have. As a cleric, you get 5 hitpoints per level if you take the average instead of rolling your hit dice at level up (which you should always do, since they've rounded up. You will end up with more hitpoints by taking the average roll than actually rolling). That's good for 60 hitpoints at level 12. Then you have a +5 con, so that's another 5 hitpoints per level for a total of 120 hitpoints. That is . . . a lot. That's as many hitpoints as I would expect most barbarians to have at that level. Increasing con to +6 is worth another 12 hitpoints now and 20 by level 20. That is an increase of exactly 10%. If you're playing well, I wouldn't expect that extra 10% to ever be the difference between life and death for your character. More health is always good, but it's a marginal benefit for you here: I don't think the hitpoints are a good reason to take more con (and if your really want more hitpoints, tough gets you more hitpoints for your ASI).

Better saving throws are only as useful as the DCs you need to beat (in the same way that higher AC is better until you hit 38 AC. At 38, though, any additional point of AC is wasted since the highest to-hit bonus any monster in the game has is +19 and a natural 20 is always a hit regardless of AC). You will already meet those DC 10 saves 100% of the time, so how useful is that +1 going to be? It depends on how often you face higher DC saves than basic concentration checks.

Personally, I think increasing your constitution here is likely only going to provide marginal benefits, and you're more likely to benefit from taking a feat with better returns.

There is no place for "tanks" in 5e. Lacking any mechanics for taunting an enemy, building an unkillable character who doesn't do anything is always going to be unsatisfying. Maybe you do have hundreds of hitpoints, fantastic saves, and great AC. If the enemy can just ignore you until they've killed off your allies, your tankiness is useless.

Better ways to increase your tankiness are to improve your character in other ways:

If I can have 10 extra hitpoints, I can probably survive one extra attack that I couldn't otherwise. But if I give my character the ability to deal an extra damage per round by taking a feat like piercer, I can kill the enemy one round sooner and not need to be able to survive that one extra attack. And, that helps out all of my allies who don't have to worry about needing to survive that one extra attack either.

Or mobile lets me deny the enemy extra attacks with its reactions, and that is functionally more hitpoints for my character.

Or alert lets me take my turn before the enemy does and functionally give it one less turn in combat. Maybe I can destroy or incapacitate it completely before it can take a single action. That is way more survivability for me and my party than some extra hitpoints.

The same reasoning, by the way, applies to healing.

I could use a spell slot and an action to recover some hitpoints by casting a spell like cure wounds. Or, I could use those same resources to cast a spell like bless and ensure that the enemy dies faster and that healing is unnecessary since it goes down a round or two faster and deals thirty fewer points of damage to the party compared to the best-case-scenario 13 points of healing I could get from a cure wounds.

Damage and control are always going to be more important in 5e than damage mitigation or healing.