How to replace SR with equivalent save bonus?

Joshua Randall · Oct 24, 2006

I don't like Spell Resistance, so I've decided to eliminate it from my campaign. I'd like to replace a given SR with a roughly equivalent bonus to saves. (Yes, I know these do not function the same way.)

For example, suppose a CR 10 creature has SR 21. A 10th level caster would need to roll an 11+ on his caster level check, meaning he has a 50% chance of success. (Not counting things like Spell Penetration.) The question is, what would be the appropriate bonus to give the CR 10 creature 50% better saves?

Before I do a lot of math to figure out what the conversion from SR to comparable save bonuses would be... has anyone already done this?

And not just for the easy cases like the one presented here, but also for the more difficult cases, like the variable, HD/level-dependent SR generated by certain spells or templates.

Thanks!

Pyrex · Oct 24, 2006

The problem is that SR is somewhat non-linear because it impacts casters differently based upon relative HD/CL of the target/caster.

A simpler method might be to just give creatures with SR the equivalent of (improved)Evasion for all three saves as follows

if (SR >= 10+HD)
{
Creature gains Improved Evasion vs Spells and SP Abilities
Creature gains Improved Mettle vs Spells and SP Abilities
}
else if (SR < 10+HD)
{
Creature gains Evasion vs Spells and SP Abilities
Creature gains Mettle vs Spells and SP Abilities
}

This preserves the inherent scaling between creatures/casters of varying HD w/o making saves impossibly good.

Cheiromancer · Oct 24, 2006

Subtract the CR from their SR and divide by 2. That should give a fair bonus.

I.e. suppose a 10th level caster casts a spell at an equal CR creature with a SR of 21. He has a 50% chance of penetrating the SR. Assume the creature also has a 50% chance of making the save (which is save negates), and the overall chance of success is 25%. You could get the same result by increasing the creature's save by +5.

I'm pretty sure that equal CR monsters are assumed to have a 50/50 chance of success saves. Otherwise this approximation goes out the window.

If the creature has a 19 SR, then the wizard has a 60% chance of penetrating it, or a 30% chance overall. Model this by increasing the creature's save by only +4. This shows that a difference of 2 SR changes the save bonus by 1.

Stalker0 · Oct 24, 2006

There are 2 kinds of spells for which removing SR will be a big change.

1) No save spells.
2) Save for half spells.

SR can block both of these, no save bonus can do that. So you may wish to take further changes other than just adding a bonus to saves.

Btw, what about SR don't you like. Perhaps it might be cleaner and easier to simply adjust SR than removing it from the game.

dvvega · Oct 25, 2006

The other thing you need to take into account is that SR can save a creature from a spell even when the caster may have tanked their Save DCs.

I'm using your CR10/SR21 creature and a 10th level caster here.

In the example of the SR 21. A 10th level caster has 50% chance of penetrating with ANY spell assuming no special feats.

This same creature would have around at least a +12 on its saving throw.

The 10th level caster can cast 5th level spells so would have a minimum of 15 in the primary attribute and thus Save DCs would be 17.

So against the caster it has 50% of not being affected and if it is it has an 80% chance of avoiding the effects. That 80% goes down with the save DCs obviously. This works out to a 90% survival rate against the spell (if my maths is correct) overall.

Now we remove its spell resistance it has a flat 80% chance of survival. Now it isn't as easy as saying +2 is fine since you must take into account that a natural 1 is always a failure. So a +4 would be more appropriate (never use odd numbers IMHO). So with a +4 the creature in question can only fail on a 1, that's a 5% failure rate.

However as previously pointed out, the spell resitance ability allows you to ignore "no save" spells, and a lot of spells have effects if you save and spell resistance ignores those.

The only way I can currently think of to leave to it close mathematically is to subtract 2 from their saving throws but give them two saving throws. If they make the first one they can apply evasion/mettle/etc and ignore everything. If they don't make the first one then they get the normal saving throw.

In addition they can save against "no save" spells if they originally had an SR clause.

Although this looks just like replacing one roll with another, a Wizard can now focus solely on Saving Throw DC improvement and get a double benefit from it. Previously he would have had to take both SR improvement and DC improvement feats to be able to get past the creature's defences.

Li Shenron · Oct 25, 2006

I don't think this is balanced at all, but something very simple could be to just turn SR into a flat +4 bonus to all saves.

A few spells have no save, so those won't be affected, but you might keep the normal SR for those alone.

Or, if the problem is calculating SR and rolls, you could just turn any SR into flipping a coin for a flat 50% chance that the spell has no effect.

Joshua Randall · Oct 25, 2006

I don't like SR because it's an unnecessary mechanic that is merely an arbitrary holdover from 1st edition. It requires additional dice-rolling (which is always bad), and it frustrates players because it makes their abilities useless roughly 50% of the time.

But, that is not the issue -- the issue is how to replace SR with a roughly equivalent save bonus -- and I've gotten some good ideas on how to do that from this thread. (I'm well aware that a saving throw does not function the same as SR.)

So, thanks to all who responded.

Stalker0 · Oct 25, 2006

Just curious, are you taking out the blur and displacement spells (they do the same thing to melee attacks).

Li Shenron · Oct 26, 2006

Joshua Randall said:
I don't like SR because it's an unnecessary mechanic that is merely an arbitrary holdover from 1st edition. It requires additional dice-rolling (which is always bad), and it frustrates players because it makes their abilities useless roughly 50% of the time.

But, that is not the issue -- the issue is how to replace SR with a roughly equivalent save bonus -- and I've gotten some good ideas on how to do that from this thread. (I'm well aware that a saving throw does not function the same as SR.)

So, thanks to all who responded.

BTW, while I think it's going to be quite frustrating to eliminate SR from the current rules, I have been thinking that your purpose makes a lot of sense. If you don't mind, I'd like to start a thread in General or Rules about the necessity of having SR in the game.

GreatLemur · Oct 26, 2006

Joshua Randall said:
I don't like SR because it's an unnecessary mechanic that is merely an arbitrary holdover from 1st edition. It requires additional dice-rolling (which is always bad), and it frustrates players because it makes their abilities useless roughly 50% of the time.

I've got to agree. SR has always been kind of annoying, and it's only gotten more glaring as the rest of the game has become more streamlined. It really does feel weirdly archaic, now (similarly: miss chances for concealment).