Should rolling a 1 on a spell saving throw double that spell's damage?

This is more of a balance question. In my table we've agreed that rolling a 20 or a 1 should be special no matter the circumstance. Spells that require attack rolls are special on crits, but, per If you roll a 1 on a saving throw against a damage spell, do you take extra damage?, spells that only require a saving throw don't.

So, as to allow spells that force the target to make a saving throw to crit, I ruled that critically failing that save causes the affected character to take double damage. This seems to me to be largely equivalent balance wise.

However, one of my players recently brought up a concern: if saving throw based spells can crit, their power level goes up dramatically, while spell attack based spells become comparably irrelevant.

Does allowing 1s to cause double damage on failed saves unbalance the game, and if so, is there something I can do that retains the "1s and 20s are special" feel without unbalancing it?

• – goodguy5 Apr 16 '18 at 17:17
• I think the Link was suppoed to be some reference that Spell Attacks crit, not what got linked. – HellSaint Apr 16 '18 at 17:17
• @HellSaint the linked question answer mentions that attack spells crit and saving throw spells don't. I believe that's what they're referring to. – goodguy5 Apr 16 '18 at 17:25
• There are three related Q&A on this topic that I recommend reading: 1 and 2 and 3 – KorvinStarmast Apr 16 '18 at 19:24

No, they shouldn't.

Does allowing 1s do double damage on failed saves unbalance the game, and if so, is there something I can do that retains the "1s and 20s are special" feel without unbalancing it?

Yes, it unbalances the game. This will make every non-caster feel sorry for their class choice as the levels go up and you will have the absolute worst time trying to make a giant horde fight against your party, because now their AoE spells actually crit.

The saving throw spells are already balanced to not crit. If you just give them the opportunity to crit, they have a tremendous boom in power, as your player noted.

Reasoning

When I say they are balanced like that, I mean by the developers and playtesting. After all, the content was published like that, and unlike some rulings (like Variant Human, which arguably highly changes the balancing of the game) there isn't even a mention on an official variant ruling allowing it. While I won't even try to argue that anything published is perfectly balanced, it is more likely that a key mechanic like this was (in average) balanced. (What I mean by in average is that there might be (there are.) underwhelming spells and overpowered spells, but the mechanic by itself is not to blame)

DPS-wise, the increase in damage is given by a multiplying factor that depends on the chance of hitting (the damage increase is more significant if the probability of hitting is lower, capped by doubling the damage if the enemy was only hit when he got a 1). Against enemies with $50\%$ chance of hitting, it is a $10\%$ increase in damage, which might not be enough to be called "tremendous", but still significant. But again, note that the harder to hit, the more significant this change is, arguably changing the most important fights. Note that a $10\%$ AoE increase in damage usually should be more significant than the same increase in single-target.

Also there is the power spike problem: As mentioned by OP, a fireball would do 56 (16d6) when critting. As a 5th lvl character. One encounter was just turned into easy roll.

Also adding another comment into the answer: Saving Throw spells don't suffer from disadvantages that Ranged Spell Attacks usually do (e.g. disadvantage at melee range).

But Spell Attacks can crit!

There is something that I let slip before: when you miss a spell attack (or any attack roll), you miss. You do zero damage. Many Saving Throw spells still do damage (usually half) when they pass the DC. So it is more evidence to argue that they are already balanced as they are. You are trading the crit chance for the guaranted damage if they dodge.

The NPCs' side

Also, as mentioned in another answer and in some comments, Player Characters are pretty squishy, mainly early game. A 5th lvl party hit by a Fireball suffers naturally. If they are hit by a critical fireball, the most squishy characters (e.g. Wizard) could even be insta-killed through double their max HP.

What can you do?

One thing you can do that doesn't completely break the system is making 1 become auto-fail and 20 become auto-success. Note that this is not standard rule.

• Huh... All this time, I thought that Nat 1 and Nat 20 were auto-fail/pass on Saving Throws (but not like "critical fail", just regular fail). – goodguy5 Apr 16 '18 at 17:33
• @goodguy5 By default, only Death Saving Throws have a special meaning to 1 and 20 (which is double-fail and double-success, respectively). Only attack rolls have auto-fail and auto-success (20 being auto-success AND critical, 1 being only auto-fail, not critical fumble). Everything else (namely Saving Throws, Ability Checks) handles 1 and 20 as any other number. – HellSaint Apr 16 '18 at 17:43
• While I agree with this answer, I feel like it needs more supporting information. How do you know that saving throw spells are balanced to not crit, for example? – Icyfire Apr 16 '18 at 17:46
• Statistically, assuming separate saves for each monster in a mob, only 1 in 20 will critically fail a save. I don't see it as a tremendous boom in power, although I agree it is a slight bump. Some math would go a great deal toward supporting your point here. – Slagmoth Apr 16 '18 at 17:52
• I think you should also point out that it is more likely to lead to party wipes if you throw spell casters at the party. The NPC's and monsters have tons of HP in this edition compared to a regular party member. – Voromir Kadien Apr 16 '18 at 18:47

Ok, four points here. For the most part, it really depends on your game and if your players are ok with punishing adventures. D&D is not like systems like 40k, where its ok to kill a player character outright with one good shot.

Damage Balance (spells by themselves)

As for increasing the raw power of a spell, it really doesn't do it that much over time. In this sense I'd call it balanced.

Consider a 3rd level Fireball, where an 11 is needed to save. I chose this spell, because for its level Wizards of the Coast has admitted to overtuning the damage to make it interesting.

Before:
The average damage done on a successful save is given by

$\textrm{Avg}_S = (4 \cdot 3.5) = 14$

The average damage done on a failed save is given by

$\textrm{Avg}_F = (8 \cdot 3.5) = 28$

Thus the average damage is given by

$\textrm{Avg} = \frac{1}{2} \cdot \left(14 + 28 \right) = 21$

If you included a 1/20 crit rule then

The average critical damage is given by

$\textrm{Avg}_C = (16 \cdot 3.5) = 56$

The average damage on failed and succesful saves remains the same, but the probability of a failed (non-critical) save decreases from $\frac{10}{20}$ to $\frac{9}{20}$.

Thus the new average damage is given by

$\textrm{Avg} = \frac{1}{20}\cdot(56) + \frac{9}{20}\cdot(28) + \frac{10}{20}\cdot(14) = 22.4$

As you can see you only increased the average fireball damage by about 1.4 per target.

One-Shot Balance

If you consider the impact of a failure for characters at 5th level, a crit failure could potentially mean instant death... whereas a regular failure would mean you might just drop them to 0 HP.

Failing:
$8\mathbf{d}6 = 3.5 \cdot 8 = 28$
Crit Failing is essentially twice that:
$56$

A 14 con wizard who rolls average health will have: 30 health. IF they roll average. For point buy, a fireball is already in danger of dropping them to 0 HP. Twice that could potentially insta-kill that character. (If damage reduces you to 0 HP and the remaining damage exceeds the character's max HP, you die instantly, without making death saving throws.)

In this sense I'd also call it unbalanced - at least at the level certain spells are introduced. It could also lead to easier TPKs because your party's healer accidentally died instantaneously at the beginning of a fight and your party wasn't expecting it.

Save Balance

Does it make sense to double damage someone with a potential 16d6 fireball if, say, their Dex save is a base of 8 and the spell save DC is only 16?

In this sense I'd call it unbalanced.

If they rolled a total higher than half the spell save DC - Why should I suffer the same damage rolling a 9 (because I've got a 20 Dex and am proficient) where another character could roll a 2 (not proficient with 12 Dex). At worst, if I were to implement something like this in my games, your total on the roll would need to be less than half of the spell save DC before an auto 1 could crit. Would give the death feel you're looking for while not hosing those who are proficient.

Thematics

Does it even make sense to crit someone with certain spells?

Personally, I'd say no. The spell damage is supposed to cover how much more or less you got clobbered by a spell.

A few important interactions

Finally, what about paralyzed creatures? (They normally auto-fail Dex Saves.)

Should they get the double crit damage too, where archers would not? Spell interactions alone are the one main reason I wouldn't allow this, as things like Stunning Strike and Hold Person/Monster would now hold all the weight in the world, when traditionally they only really help melee. Sorcerers' Metamagic especially would and could become extremely potent; evocation wizards' maximizing damage from Overchannel, and divination wizards' Portents become brutal (especially combined with things like the Disintegrate spell).

Some alternative options if you want nat. 1s rolled for saves to feel special

• If the character is resistant to the damage, remove the resistance for that casting of the spell. (Doesn't alter the damage of the spell, just the amount the character expects to take.)

• You could cause the damage roll to reroll 1s for free as per the
feat in the PH that does the same. (This actually helps the damage
lot.)

• Require the total of the roll to be less than half the target save DC.

• Attach a sort of stun to the character or dazed. Whereby their next offensive round of offensive abilities with the next minute either has disadvantage or creatures gain advantage on the next save for spells cast by this character (makes it even for casters and doesn't discriminate on type of spell). (Losing action economy on a damaging thing can at least make the 1 painful while not totally boning the player, and if the situation is dire they can risk resources on spells to save the day.)

• I know this isn't OP's question, but how would implementing both double damage on nat. 1s and zero damage on nat. 20s on saving throws affect the math? – V2Blast Apr 16 '18 at 19:14
• I'm not a full blown mathmatician but I've done enough with average formula's in the AI field. Ideally it should bring it back in line some. But rounding will probably not make it identical. Assuming a 11 is needed to save: Traditional Fireball = 28 Augmented Fireball 1/20 * 16 * 3.5 + 1/20 * 0 + 9/20 * 8 * 3.5 + 9/20 * 4 * 3.5 = 2.8 + 0 + 12.6 + 6.3 = 21.7 – Spoo Apr 16 '18 at 19:37
• Sorry my comment should say traditional fireball is 21. It's only 28 if you know they fail their save already. So regular fireball 21. Ended crit range fireball 22.7 – Spoo Apr 16 '18 at 19:47
• DND is not like systems like 40k where its ok to kill a player outright with a good shot That's not true. I have seen three D&D 5e characters die from a one shot (character death) at levels 1 and 2 from critical hits that rolled high. Almost lost another one that way last month, but inspiration saved the day for a re roll. – KorvinStarmast Apr 16 '18 at 19:55
• I should apologize. The levels 1-3ish are brutal I grant you. But outside of that the rest of the game is not like that if you follow it by raw. Outside of that though, the rest of the game does a good job of not burdening you with save or die tactics. (At least not in one round.) I make no claims over level 9 spells though. But most of the damaging ones are nice enough to do < twice your total hp. 40k) I've seen characters just suddenly disappear because the 'critical effect' killed them instantly and caused tertiary damage killing others around them. And the weapon used is common. – Spoo Apr 16 '18 at 19:58