D&D 5E Sell/unsell me on Magic Resistance and Legendary Resistance

[FormerlyHemlock]

When it comes to Magic Resistance, I realize this is the simplified Spell Resistance.

But it still feel like a blanket "cheat code". Advantage means a demon, say, with 50% chance of making a save now has a 75% chance.

It basically means spellcasters are screwed. Go do something indirect instead, like raise a wall, or buff a party member. Or stay in the background pew-pewing your cantrips.

*snip*

Should Magic Resistance be limited to the initial save only?

What do you think?

Huh. From the thread title I expected you to go in the other direction--observing that Magic Resistance in 5E is incredibly weak and near-pointless compared to AD&D % Magic Resistance. 5E Magic Resistance is zero help against Wall of Force, Maze, Otto's Irresistible Dance, or even Eldritch Blast/Scorching Ray. One of my first 5E experiences was when I got to watch a Mind Flayer and a bunch of drow get roasted to death by (of all things) a 9th level Fireball cast by (moronic) 22nd(?) level cleric/mage (11/11 I think? definitely at least 9/9). It was extremely disconcerting to me as a grognard to see an illithid, of all things, die to a Fireball.

I've considered bringing % Magic Resistance back into the game but each time I decide that it's just a bit too far outside the 5E idiom, and that if I want that experience I should really be playing AD&D.

 

[bgbarcus]

I've considered bringing % Magic Resistance back into the game

I had the same urge when I started 5e, MR seemed ridiculously weak. Then I realized the big limiting factor on spellcasters is that they have so few spell slots. When a wizard casts a spell they are using a limited resource so it should have a good chance of having some effect. I've also noticed the monsters getting far more deadly in higher levels. Rather than seeing PC's turn into unstoppable godlings they are looking very breakable at 10th level. If a battle against a legendary monster goes beyond round three, a big sudden ending is needed or there is a good chance at least one PC will go down.

 

[CapnZapp]

Advantage/Disadvantage equals approximately +/-3.5 which is roughly a 17% adjustment on a d20. Anydice.com makes it fairly easy to see the effect.

Then you'd see that the probability increase varies. The average increase is indeed what you say, but that doesn't tell the whole story.

Advantage gives a much stronger benefit when the original benefit is around 50-50; and doesn't give much of a benefit at all if you only miss on a 20, and when you only hit on a 20.

The benefit at 50% is, as I stated, +25% for 75%.

The true design strength of advantage lies in how it benefits the most interesting situations the most, while still not turning the outlier into an extreme case. By this I mean that a regular +3 bonus benefits the average attack and the extremely optimized attack equally. Advantage gives a huge boost to the average attack while helping the extremely optimized not much at all.

Put simply, the advantage mechanism gives diminishing returns for the minmaxer - all because it does notequal a straight +17% bonus.

 

[CapnZapp]

I'm not a fan of Magic Resistance, but for the opposite reason: I feel it's not strong enough. Spells that don't allow saves ignore it, meaning that you always have an "out" against those creatures. Creature has Magic Resistance: use Scorching Ray instead of Fireball. At first I considered giving Magic Resistance actual Resistance to Magic Damage, but that came off as reducing the point of other Resistances. I'm currently considering having Magic Resistance give Disadvantage on Magic Attacks as well.

I think you mean you want "spell resistance" that resists all spells equally.

I consider Magic Resistance to be strong against spells with save DC, extremely strong against spells that you want the monster to fail repeated saves.

But I obviously realize it is "weak" (nonfunctional) against spells without saves.

I would have the two categories meet, much like you want, but perhaps at a lower power level.

In fact, I'm thinking about tweaking both legendary and magic resistance into something unified.

 

[famousringo]

Advantage/Disadvantage equals approximately +/-3.5 which is roughly a 17% adjustment on a d20. Anydice.com makes it fairly easy to see the effect.

Not sure what math you're using, but it's not right.

To simplify, imagine we're rolling 2d4 instead of 2d20 to get our 50% chance. The size of the dice won't change the effect. There are 16 possible outcomes of 2d4, but if you get a 3 or 4 on either of them, you win. That means you only fail on 1 and 1, 1 and 2, 2 and 1, or 2 and 2. The other 12 outcomes of 16 succeed, therefore 75% chance of success.

At some probability of success, advantage will be equivalent to ~+3.5, but at 50%, advantage is effectively +5.

 

[Sunseeker]

I'm not saying "have no extra defense".

I want to hear your opinion on Wotc's specific implementations.

Specifically I think it works well in practice. It reduces the risk that higher level monsters are going to be decimated by a single spell, but at the same time, it's obviously a reaction to the fact that spellcasting is comparatively overpowered. It is needed for another reason though: Monsters have no class skills. In combat this makes them fairly boring and also incredibly predictable. EX: I've given some dragons levels in barbarian. Absolutely changes the feel of the fight because the number of things most creatures can do can be counted on one hand, often with a finger left over. Players are the complete opposite, they may have lower HP, but they have a dozen different things they can do in battle. Toss 5 of them on the board and that's thousands of possible combinations.

I think it's a good rule, but only insomuch that it's the rule they needed to counter for the fact that high-level magic is absurd.

 

[CapnZapp]

Specifically I think it works well in practice. It reduces the risk that higher level monsters are going to be decimated by a single spell, but at the same time, it's obviously a reaction to the fact that spellcasting is comparatively overpowered. It is needed for another reason though: Monsters have no class skills. In combat this makes them fairly boring and also incredibly predictable. EX: I've given some dragons levels in barbarian. Absolutely changes the feel of the fight because the number of things most creatures can do can be counted on one hand, often with a finger left over. Players are the complete opposite, they may have lower HP, but they have a dozen different things they can do in battle. Toss 5 of them on the board and that's thousands of possible combinations.

I think it's a good rule, but only insomuch that it's the rule they needed to counter for the fact that high-level magic is absurd.

But do your players agree.

You only have a single slot of your highest spell level. You would hate that go to waste.

Seeing the monster save is bad enough. Have the DM casually deflect it is much worse.

I don't see a solution that doesn't involve telling the players about the monster's three legendary saves; which makes for a very meta game.

I would much rather have the monster make its saves fair and square. And instead have incredible powers of shrugging of spell effects; even ones that normally are fatal or permanent.

 

[crashtestdummy]

Not sure what math you're using, but it's not right.

To simplify, imagine we're rolling 2d4 instead of 2d20 to get our 50% chance. The size of the dice won't change the effect. There are 16 possible outcomes of 2d4, but if you get a 3 or 4 on either of them, you win. That means you only fail on 1 and 1, 1 and 2, 2 and 1, or 2 and 2. The other 12 outcomes of 16 succeed, therefore 75% chance of success.

At some probability of success, advantage will be equivalent to ~+3.5, but at 50%, advantage is effectively +5.

To make it mathematically precise, simply calculate the probability of failure. That is, the chance that both rolls fail to reach the required DC.

If the success chance is 20%, the probability of failure is 0.8. With advantage, the probability of failure is 0.8x0.8=0.64. That is, a 36% chance of success.
If the success chance is 30%, the probability of failure is 0.7. With advantage, the probability of failure is 0.7x0.7=0.49. That is, a 51% chance of success.
If the success chance is 40%, the probability of failure is 0.6. With advantage, the probability of failure is 0.6x0.6=0.36. That is, a 64% chance of success.
If the success chance is 50%, the probability of failure is 0.5. With advantage, the probability of failure is 0.5x0.5=0.25. That is, a 75% chance of success.
If the success chance is 60%, the probability of failure is 0.4. With advantage, the probability of failure is 0.4x0.4=0.16. That is, a 84% chance of success.
If the success chance is 70%, the probability of failure is 0.3. With advantage, the probability of failure is 0.3x0.3=0.09. That is, a 91% chance of success.
If the success chance is 80%, the probability of failure is 0.2. With advantage, the probability of failure is 0.2x0.2=0.04. That is, a 96% chance of success.

As can be seen, the change in probability is dependent on the initial success chance and is not constant.

 

[CapnZapp]

Not sure what math you're using, but it's not right.

To simplify, imagine we're rolling 2d4 instead of 2d20 to get our 50% chance. The size of the dice won't change the effect. There are 16 possible outcomes of 2d4, but if you get a 3 or 4 on either of them, you win. That means you only fail on 1 and 1, 1 and 2, 2 and 1, or 2 and 2. The other 12 outcomes of 16 succeed, therefore 75% chance of success.

At some probability of success, advantage will be equivalent to ~+3.5, but at 50%, advantage is effectively +5.

The number he's using is correct, but only as an average. See my post, above.

The easiest way to see how advantage turns a 50% chance into 75% is to forget about dice and instead flip a coin.

One coin gives the outcomes "heads" or "tails". Two outcomes, 50% each. Simple.

Two coins gives the outcomes

• heads and heads
• heads and tails
• tails and heads
• tails and tails

If "heads" means "success", it should be trivial to see that three out of the four possible outcomes mean at least one success.

And three out of four = 75%

 

[Sunseeker]

But do your players agree.

I'm gonna sound like a jerk for a second but: I don't really care if they think it does or doesn't. They're not running the game. They don't have a thousand things running through their mind. Their only concern is their potential victory or loss, not if the system works as intended.

You only have a single slot of your highest spell level. You would hate that go to waste.

And I only have one BBEG for them to fight. They're not going to get to do their cool stuff if the wizard walks in the room and neuters the BBEGs brain turn 1.

Seeing the monster save is bad enough. Have the DM casually deflect it is much worse.

Tough! That's what makes the bad guy scary. Not just when he saves, but when saving for him isn't even so much exertion as a flick of the wrist. That's what tells the players this guy means business.

I don't see a solution that doesn't involve telling the players about the monster's three legendary saves; which makes for a very meta game.

Meh, most of my players are DMs anyway, so they know which monsters have legendaries. I don't put the kibosh on meta talk, provided it's not becoming a distraction to fluid play.

I would much rather have the monster make its saves fair and square. And instead have incredible powers of shrugging of spell effects; even ones that normally are fatal or permanent.

What? I don't even know how to respond to this statement. You want them to get a single die roll, have nothing that can affect that die roll (aside from modifiers) but then somehow have some other ability that lets them shrug off magical effects? How is that different? Magic resistance, legendary resistance, that is EXACTLY what they do. The reason they are preemptive to the spell effects rather than reactive to the spell effects is simply because some effects, like I mentioned with Feeblemind, are essentially SoD. There is no "effect to shrug off", their intellect just got turned into pudding.

The purpose of Magic Resistance and Legendary Resistance is completely outside the statistical impact. It's to allow the DM to control the flow of a game without being subject to powerful players with impossible saves making continued play pointless.