Your encounter generator is not displaying difficulty correctly - A given monster added to some encounter should not count towards the (amount of monsters multiplier) if said monster is significantly below the average CR of the encounter. Whether a monster is significantly below the average CR is as of now a grey-zone, however it's clear that a given encounter doesn't get significantly harder if we add a CR 1/2 skeleton to an Ancient Dragon encounter, which your encounter generator says it does by increasing the adjusted XP as if the skeleton added some significant problem.
I just experimented with two other online encounter calculators - including both the "most well known" one, Kobold Fight Club, and a lesser-know one I personally like. In both, I set up an encounter between four level 20 PCs and an Ancient Brass Dragon. The latter is CR 20, so it's a Medium encounter. I then added a single CR 1/2 Skeleton to the mix, and both changed the difficulty to Hard.
Simply put, in this case the issue is not a DDB issue. It's just a quirk in how the CR and encounter formulae work in 5e. It's up to the DM to use common sense, and not to blindly trust the numbers. (Also, for whatever it's worth, this is not an issue unique to 5e; I recall a Pathfinder 1e book cautioning against throwing a huge number of goblins at a high-level party just because CR numbers said it would be a fair fight, without realizing that CR breaks down if the individual monsters are way outside the players' level.)
I agree that it's not an issue only DDB has, however it's clearly stated in Dungeon Master's Tools - even on DDB for encounter calculations: https://www.dndbeyond.com/sources/basic-rules/building-combat-encounters - "When making this calculation, don’t count any monsters whose challenge rating is significantly below the average challenge rating of the other monsters in the group unless you think the weak monsters significantly contribute to the difficulty of the encounter". So I don't think: ' its a quirk in how the CR and encounter formulae work '. That being said this can be circumvented with common sense and a experienced DM, however it becomes much more difficult to evaluate when encounters aren't that obvious. Lets say: 1x CR 15, you add 1x CR 10, should the total then multiplied, how about a CR 9, 8 ? This becomes much more unclear and thus is would be nice to have a general guide-line. I believe this is something DDB has the capability to establish.
It's not possible to make a hard and fast formula for this; it depends too much on the circumstances of the encounter and the individual monsters.\
Also, D&D 5's bounded accuracy means that low-level critters can be more relevant than they are in other editions.
If the monster isn't relevant to the fight, just don't put it into the encounter. There's nothing wrong with describing all the guards/skeletons/other mooks who flee in terror, get scattered in their wake without contributing to the fight, or go down in the first fireball.
I believe this is something DDB has the capability to establish.
Alas, I believe you have far too much faith. The number of bugs that have existed for 3+ years without being fixed is not small. Some of these were stated to be on the roadmap to be fixed back in 2020-ish, but these days it's impossible to even get anyone in power to acknowledge their existence. It's as if the devs these days want to pretend they do not exist.
Worse, there exist some "text bugs" (as in, bits of text that provide incorrect information about how features work - so they're very important because they're effectively lying to players about the rules, but they have nothing mechanical tied to them). Some of these have existed for years - and these are especially egregious because fixing them would not even require re-coding anything. It would literally require 5 seconds of retyping some text.
If for three years and counting the devs are still unwilling or unable to change one numeral and delete two words in a text snippet, I fear establishing what you suggest is probably way outside their wheelhouse.
The calculator also doesnt take into account quantity of enemies. I loaded up 12 goblins for a party of 5 lvl 4s and got a 600 xp output listing it as easy. 14 goblins became medium at 700 xp. The calculator did not include the X3 for the amount of enemies which would have bumped the XP to 1800 or a hard rating.
For the same party a young green dragon is listed as medium even tho the XP limit for the party should be 2500 compared to the 3900 for the dragon making this a deadly encounter.
The calculator also doesnt take into account quantity of enemies. I loaded up 12 goblins for a party of 5 lvl 4s and got a 600 xp output listing it as easy. 14 goblins became medium at 700 xp. The calculator did not include the X3 for the amount of enemies which would have bumped the XP to 1800 or a hard rating.
I’m kinda laughing (not at you, but just at the situation)—because this is EXACTLY the example I alluded to from the Pathfinder book.
By the formulae, a large number of weak monsters may post a threat to a higher-level party—but the formulae can’t take certain factors into account. One of those factors is that a single Fireball or such from a higher-level character can wipe out most of the encounter in a single turn. Which is fine if your goal is just to incentivize the players to burn resources—but at a certain point you’re not really increasing the difficulty or the danger by adding more weak monsters, and no formula can really account for this.
I fear you may be correct. The calculator is just really off - which is a little frustrating if you wish to really push players to the edge, without a TPK. I've experimented in our group to test what the adjusted XP should be for an encounter to actually be deadly according to a self-made rating system. For our group the adjusted XP should be about 1.2 - 1.6 * Daily Budget for our group to consider it deadly. However this metric becomes completely non-sensical when we are talking boss fights (against a single monster). We are 6 players which means the adjusted XP for a single monster is half of what the monster actually gives in XP (As the XP calculator is primarily focused on parties of size 3-5). This in turn means that by this metric our party of 6 x lvl 10 should be matched against a single monster of CR 25 - 30 which is of course non-sensical and would result in a TPK. This big offset of course comes from testing encounters with a vast amount of monsters which means the adjusted XP has been multiplied - just incorrectly because some monster doesn't contribute enough to be considered in the multiplier which DDB ignores. Therefor i feel as though it is trivial to make it better but of course almost impossible to make perfect.
The combat encounter calculates encounter difficulty exactly per the rules laid out in the Dungeon Master's Guide/Basic Rules. While the rules say
When making this calculation, don’t count any monsters whose challenge rating is significantly below the average challenge rating of the other monsters in the group unless you think the weak monsters significantly contribute to the difficulty of the encounter.
They do not say what counts as 'significantly below' so there is no way for the encounter tool to make that decisions.
That's because it's down to the DM to decide.
If you think a monster is significantly below the the average challenge rating of the other monsters, you don't add it to the encounter until after you've determined the encounters difficulty. Then you add those 'significantly below' monsters and save the encounter.
The exact point of the formula including multiplying xp based on number of enemies in the encounter is to give an idea of the approximate difficulty to the average party. If the party doesnt have a spellcaster or that spell caster didnt pick up fireball the quick solution is out. A frontliner taking 8-12 hits per turn at level 4 on the off chance they all overcome AC (adding in flanking rules to give each attack advantage which I do even for the monsters) could end the parties chances of survival quickly. Once the frontliner is down midrange and spell casters are going to be eating attacks left and right with typically lower AC thresholds. A strategic DM that decided it was better to gang up on one character at a time instead of evening out across all players then throw in a couple of really unlucky rolls for the party and you could have them down and dead in a couple of rounds. Queue the calculator reminding you that was a harder fight because of quantity and not because it was low CR monsters.
And of course a higher level party would have a lower difficulty rating even with the multiplication for quantity because thats how the calculation is designed to work. What would be considered medium at level 4 is almost always not medium at level 5. Just because one party would find an encounter easy doesnt mean they all would so the calculators should use the formula that is provided with the guides and let the DM decide what to do from there. This is even more true now that so many new people are joining the game and trying to create their own encounters without actually playing the game before hand. They need to see in plain text that what they have read in the Guidebooks is what is being used by online calculators or they may become confused.
the encounter bulder does take the amount of enemies into account. this is marked under the adjusted XP and that's the on taken into account when saying the dificulty rating
Your encounter generator is not displaying difficulty correctly - A given monster added to some encounter should not count towards the (amount of monsters multiplier) if said monster is significantly below the average CR of the encounter. Whether a monster is significantly below the average CR is as of now a grey-zone, however it's clear that a given encounter doesn't get significantly harder if we add a CR 1/2 skeleton to an Ancient Dragon encounter, which your encounter generator says it does by increasing the adjusted XP as if the skeleton added some significant problem.
To be fair, this is not an issue specific to DDB.
I just experimented with two other online encounter calculators - including both the "most well known" one, Kobold Fight Club, and a lesser-know one I personally like. In both, I set up an encounter between four level 20 PCs and an Ancient Brass Dragon. The latter is CR 20, so it's a Medium encounter. I then added a single CR 1/2 Skeleton to the mix, and both changed the difficulty to Hard.
Simply put, in this case the issue is not a DDB issue. It's just a quirk in how the CR and encounter formulae work in 5e. It's up to the DM to use common sense, and not to blindly trust the numbers. (Also, for whatever it's worth, this is not an issue unique to 5e; I recall a Pathfinder 1e book cautioning against throwing a huge number of goblins at a high-level party just because CR numbers said it would be a fair fight, without realizing that CR breaks down if the individual monsters are way outside the players' level.)
I agree that it's not an issue only DDB has, however it's clearly stated in Dungeon Master's Tools - even on DDB for encounter calculations: https://www.dndbeyond.com/sources/basic-rules/building-combat-encounters - "When making this calculation, don’t count any monsters whose challenge rating is significantly below the average challenge rating of the other monsters in the group unless you think the weak monsters significantly contribute to the difficulty of the encounter".
So I don't think: ' its a quirk in how the CR and encounter formulae work '. That being said this can be circumvented with common sense and a experienced DM, however it becomes much more difficult to evaluate when encounters aren't that obvious. Lets say: 1x CR 15, you add 1x CR 10, should the total then multiplied, how about a CR 9, 8 ? This becomes much more unclear and thus is would be nice to have a general guide-line. I believe this is something DDB has the capability to establish.
It's not possible to make a hard and fast formula for this; it depends too much on the circumstances of the encounter and the individual monsters.\
Also, D&D 5's bounded accuracy means that low-level critters can be more relevant than they are in other editions.
If the monster isn't relevant to the fight, just don't put it into the encounter. There's nothing wrong with describing all the guards/skeletons/other mooks who flee in terror, get scattered in their wake without contributing to the fight, or go down in the first fireball.
Alas, I believe you have far too much faith. The number of bugs that have existed for 3+ years without being fixed is not small. Some of these were stated to be on the roadmap to be fixed back in 2020-ish, but these days it's impossible to even get anyone in power to acknowledge their existence. It's as if the devs these days want to pretend they do not exist.
Worse, there exist some "text bugs" (as in, bits of text that provide incorrect information about how features work - so they're very important because they're effectively lying to players about the rules, but they have nothing mechanical tied to them). Some of these have existed for years - and these are especially egregious because fixing them would not even require re-coding anything. It would literally require 5 seconds of retyping some text.
If for three years and counting the devs are still unwilling or unable to change one numeral and delete two words in a text snippet, I fear establishing what you suggest is probably way outside their wheelhouse.
The calculator also doesnt take into account quantity of enemies. I loaded up 12 goblins for a party of 5 lvl 4s and got a 600 xp output listing it as easy. 14 goblins became medium at 700 xp. The calculator did not include the X3 for the amount of enemies which would have bumped the XP to 1800 or a hard rating.
For the same party a young green dragon is listed as medium even tho the XP limit for the party should be 2500 compared to the 3900 for the dragon making this a deadly encounter.
I’m kinda laughing (not at you, but just at the situation)—because this is EXACTLY the example I alluded to from the Pathfinder book.
By the formulae, a large number of weak monsters may post a threat to a higher-level party—but the formulae can’t take certain factors into account. One of those factors is that a single Fireball or such from a higher-level character can wipe out most of the encounter in a single turn. Which is fine if your goal is just to incentivize the players to burn resources—but at a certain point you’re not really increasing the difficulty or the danger by adding more weak monsters, and no formula can really account for this.
(Obligatory mention that the inverse can also be true: https://media.wizards.com/2014/downloads/dnd/TuckersKobolds.pdf)
I fear you may be correct. The calculator is just really off - which is a little frustrating if you wish to really push players to the edge, without a TPK. I've experimented in our group to test what the adjusted XP should be for an encounter to actually be deadly according to a self-made rating system. For our group the adjusted XP should be about 1.2 - 1.6 * Daily Budget for our group to consider it deadly. However this metric becomes completely non-sensical when we are talking boss fights (against a single monster). We are 6 players which means the adjusted XP for a single monster is half of what the monster actually gives in XP (As the XP calculator is primarily focused on parties of size 3-5). This in turn means that by this metric our party of 6 x lvl 10 should be matched against a single monster of CR 25 - 30 which is of course non-sensical and would result in a TPK. This big offset of course comes from testing encounters with a vast amount of monsters which means the adjusted XP has been multiplied - just incorrectly because some monster doesn't contribute enough to be considered in the multiplier which DDB ignores. Therefor i feel as though it is trivial to make it better but of course almost impossible to make perfect.
The combat encounter calculates encounter difficulty exactly per the rules laid out in the Dungeon Master's Guide/Basic Rules. While the rules say
They do not say what counts as 'significantly below' so there is no way for the encounter tool to make that decisions.
That's because it's down to the DM to decide.
If you think a monster is significantly below the the average challenge rating of the other monsters, you don't add it to the encounter until after you've determined the encounters difficulty. Then you add those 'significantly below' monsters and save the encounter.
Find my D&D Beyond articles here
The exact point of the formula including multiplying xp based on number of enemies in the encounter is to give an idea of the approximate difficulty to the average party. If the party doesnt have a spellcaster or that spell caster didnt pick up fireball the quick solution is out. A frontliner taking 8-12 hits per turn at level 4 on the off chance they all overcome AC (adding in flanking rules to give each attack advantage which I do even for the monsters) could end the parties chances of survival quickly. Once the frontliner is down midrange and spell casters are going to be eating attacks left and right with typically lower AC thresholds. A strategic DM that decided it was better to gang up on one character at a time instead of evening out across all players then throw in a couple of really unlucky rolls for the party and you could have them down and dead in a couple of rounds. Queue the calculator reminding you that was a harder fight because of quantity and not because it was low CR monsters.
And of course a higher level party would have a lower difficulty rating even with the multiplication for quantity because thats how the calculation is designed to work. What would be considered medium at level 4 is almost always not medium at level 5. Just because one party would find an encounter easy doesnt mean they all would so the calculators should use the formula that is provided with the guides and let the DM decide what to do from there. This is even more true now that so many new people are joining the game and trying to create their own encounters without actually playing the game before hand. They need to see in plain text that what they have read in the Guidebooks is what is being used by online calculators or they may become confused.
the encounter bulder does take the amount of enemies into account. this is marked under the adjusted XP and that's the on taken into account when saying the dificulty rating