Monster's Saves

Hi all, I'm writing today with a question regarding the intentions of Monster's Saves. I'm a player in the campaign of another forum member (he asked about toxins and I was the one bringing it up :D).

When researching the problem I was seeking toxin for (read. half a dozen Griffons being entirely conscious and not tied up and making us piles of money) he said (in character) that due to the size of the Griffons, 2 doses would be required in order for it to be effective.

At the time I didn't even blink (it's perfectly reasonable) but thinking about it later I was wondering if maybe the save for monsters had that sort of consideration built in (via higher save chance). 

So I'm asking here before even bothering him, I'd like to basically know the intention behind Monster Saves as to whether things like bulk/resistance to poison due to size were included in each Monster's Save stat or whether it's simply a function of HD.

If it was intended to be included, I'll mention it to him (but how he wants to implement it is always up to him) but given this is my plan I feel it's my job to see that my party has the best chances of being unmolested by Griffons.

Lairs and Encounters tells us that monster saving throws are both a function of their type (undead, fantastic creature, beastman, etc) and their HD.

It does not include a modifier for their size, body shape, BMI, or other measure of mass.

So monster saving throws likely do include some consideration for natural resistance to things like poison based on their type, but it would be entirely reasonable for monsters to have specific variations.

So, monster weight/mass is influenced by HD (weight is (HD * 10)^BME, where BME is a sort of base indication of how ferocious a monster may be for it's size).

In theory, then, the ability of a larger monster to save more effectively versus a "generic" dose of a poison is somewhat already there, though many monsters have better or worse saves than a Fighter of the same HD - it's not at all linear, not even within the same monster category.

The general gist, though, yea, one would expect a larger dose of poison to work better (or, at some point, kill the creature even if it's not meant to) because poison (generally) is based on biological and chemical functions. That'd include needing a larger dose to affect a larger creature.

In general, the supply cost of a creature quadruples every size category.

So, poisoning a griffon (Large) instead of a man (Medium) could take 4 doses to get the same effect, and underdosing the creature may give a bonus to the save (conversely, overdosing would give a penalty)

Highly conjecturally and assuming I didn't screw this up, one could make a guess as to what underdosing or overdosing may due to a saving throw. If we assume for the moment that dosing a creature 4 times causes 4 saves, and additionally it only takes one failure to cause the poison to take effect, we can basically calculate the save chance as (4d20 take lowest).

Dose a 4th level Fighter 4 times. That's 4 saves; and any failure gets him. The chance to save is (4d20 take lowest, at least 12+). The Fighter 4 saves vs poison on a 12+; a 45% chance to make it.

If he gets 4 chances to make the save, he's got only a 4% chance (45%^4). 3 chances is 9%, 2 chances is 20%. 

That's how it works now, if you poison somebody 4 times at once.

If we map that to a single roll, that's about a -8, -7, or -5 to a single d20 roll, for four, three, and two doses, if we take that multiplicative chance as a flat chance. 

Conversely, our Griffon fails a save on an 11-. That's a 55% chance. If any failure dooms the griffon, it's toast. Underdosing the griffon (3, 2 or 1 doses out of a 4 dose requirement) takes us to 30%, 16%, and 9% - or a +5, +8 or +9 on a single d20.

After about 6-7 doses off low or high the whole thing asymtotically approaches -9/+11, making it a 100% chance of success or failure. The table is different for every save value from F0 (15+) to F21 (1+) and is essentially the same sort of thing as 5E's Advantage mechanic - middling values benefit the most.

This'd probably make more sense if poison was "save or half" for whatever it's effect; then you could figure out a "save or nothing" value at the very low end of required dosages.



This post warmed my heart. Great analysis!


Upon review, the supply cost multiplier from Man-Sized to Large is wrong - should be x8. I'm not really sure where I got x4 from?

However, one could do either supply cost multipliers, or, perhaps to be easier, the unit sizing from D@W:

  Herbivore/Omnivore Carnivore Unit Sizing
Size Supply Cost Multiplier Supply Cost Multiplier # of Men Multiplier
Man-Sized 0.5   2   1  
Large 4 8 16 8 2 2
Huge 12 3 48 3 6 3
Gigantic 48 4 192 4 24 4
Colossal 240 5 960 5 120 5


Unit sizing makes the scope of the whole thing a lot smaller. Dunno. I'll work this out and post something later on.

Randomly, one interesting thing about doing something like this is that you could invoke a "potency" score for various poisons - maybe dragon blood is worth a single Huge Dose.

A median lethal dose rating, basically. Water is poisonous at a certain dosage level.

So something like an LD50 (the Lethal Dose for 50% of whatever is being subjected to it). An LD50 would actually be a save at +4, though, since 0-level humans save against poison 30% of the time.


Very much like that.

What I ended up doing is giving a "size" classification to effects, so a Large Poison, or Colossal trap. If you are of the same size, or save as the same size for whatever reason, you roll a single die as normal.

If you save smaller or larger, though, you get the built-in penalties or bonuses as calculated much like 5E's Advantage mechanic works.

It seems like it should have some utility.

Mathsplosion here:

Thanks heaps for replies, I was just curious, especially when I saw the thread talking about dopplegangers with their F10 saves with only 4HD.


Thanks again koewn