I would say yes. If you are using the dragon spellcasting optional rule, then potentially not as much, but without spells, the breath weapon is the dragon's main ranged attack. It's a big part of who they are. A dragon with no breath weapon that did still have spellcasting and also a lair action may not be quite as much weakened by it, but the CR of a dragon absolutely takes the power and potential of a breath weapon into account.
It would, probably by 2-3 points using the DMG. For reference look at the Adult red dragon: it’s action can be used to A) multi attack for 56 Avg damage, or B) breathe fire for 63 avg (doubled to 126 by DMG rules for AoE). Over 3 rounds it will likely get to breathe fire 1 time, so that means (56+56+126)/3 roughly 79 damage vs a straight 56 if the breath weapon is removed. Given that the DMG table typically changes offensive CR once for every 5 DPR (damage per round) at mid/high levels that’s about a 4-5 ish change in offensive CR level. Balanced with no change to defense that should come out to about a 2-3 CR reduction overall.
thats assuming all other things remain the same (legendary actions, lair actions, other abilities) and the dragon doesn’t have spellcasting available that would change its DPR
I agree with TexasDevin that removing a breath weapon would greatly reduce the challenge of any dragon. I've had whole dragon encounters shift dramatically because the dragon got it's breath weapon recharged and could suddenly do a ton of damage to almost the entire party in one action.
As for the Shadow Dragon question, I think it would also reduce the CR by quite a bit. That action doesn't just do a lot of damage but, if successful at killing someone, turns an enemy into an ally. That's a major part of what makes that dragon so fearsome and deadly.
These are excellent things to think about when pitting a party against any dragon, and a good reason for DMs to alter stat blocks to suit their party and the kind of encounter they want to run!
An ancient red dragon does 55 damage with a claw/claw/bite routine. It does 91 to multiple targets (monster design assumes 2 targets) with a breath weapon. Over three rounds, that works out to 165 damage without using its breath weapon, 292 using its breath weapon once (it also does 171 over 3 rounds with tail attacks).
So yes, it's a reduction in CR, though how much of a reduction is a bit of work to compute.
The title's sort of self explanatory. Would removing the breath weapon of a dragon drop it’s challenge rating? By how much?
I would say yes. If you are using the dragon spellcasting optional rule, then potentially not as much, but without spells, the breath weapon is the dragon's main ranged attack. It's a big part of who they are. A dragon with no breath weapon that did still have spellcasting and also a lair action may not be quite as much weakened by it, but the CR of a dragon absolutely takes the power and potential of a breath weapon into account.
"Not all those who wander are lost"
Would the same happen if you removed a Shadow Dragon's shadow generating on death?
It would, probably by 2-3 points using the DMG. For reference look at the Adult red dragon: it’s action can be used to A) multi attack for 56 Avg damage, or B) breathe fire for 63 avg (doubled to 126 by DMG rules for AoE). Over 3 rounds it will likely get to breathe fire 1 time, so that means (56+56+126)/3 roughly 79 damage vs a straight 56 if the breath weapon is removed. Given that the DMG table typically changes offensive CR once for every 5 DPR (damage per round) at mid/high levels that’s about a 4-5 ish change in offensive CR level. Balanced with no change to defense that should come out to about a 2-3 CR reduction overall.
thats assuming all other things remain the same (legendary actions, lair actions, other abilities) and the dragon doesn’t have spellcasting available that would change its DPR
I agree with TexasDevin that removing a breath weapon would greatly reduce the challenge of any dragon. I've had whole dragon encounters shift dramatically because the dragon got it's breath weapon recharged and could suddenly do a ton of damage to almost the entire party in one action.
As for the Shadow Dragon question, I think it would also reduce the CR by quite a bit. That action doesn't just do a lot of damage but, if successful at killing someone, turns an enemy into an ally. That's a major part of what makes that dragon so fearsome and deadly.
These are excellent things to think about when pitting a party against any dragon, and a good reason for DMs to alter stat blocks to suit their party and the kind of encounter they want to run!
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An ancient red dragon does 55 damage with a claw/claw/bite routine. It does 91 to multiple targets (monster design assumes 2 targets) with a breath weapon. Over three rounds, that works out to 165 damage without using its breath weapon, 292 using its breath weapon once (it also does 171 over 3 rounds with tail attacks).
So yes, it's a reduction in CR, though how much of a reduction is a bit of work to compute.
No, not really.
Just put x10 the damage output of bite/claw/tail
x2 number of spells
x10 number of dragon support creatures (mages,clerics,warlocks,etc)
x10 the number of traps in the lair
x10 number of dragons (younger)
or all of these? try it , lol