D&D 5E Dragon's breath weapon vs wall

[Umbran]

First, your units are mismatched. You're talking about hp for sections of wall and damage from a single attack that may or may not strike multiple sections of wall. I would consider how many sections of wall would be struck by the dragon's breath and compare the hp total with the breath damage.

But, that's not normally how area of effects work - nomrally each target within the area takes full damage.

Or, have you been having a dragon breathe on the PCs, and divide the damage among them?

However, this probably applies:

"Damage Threshold: Big objects such as castle walls often have extra resilience represented by a Damage Threshold. An object with a Damage Threshold has immunity to all damage unless it takes an amount of damage from a single Attack or effect equal to or greater than its Damage Threshold, in which case it takes damage as normal. Any damage that fails to meet or exceed the object’s Damage Threshold is considered superficial and doesn’t reduce the object’s Hit Points."

Set the damage threshold in a place where dragonfire or typical siege engines may or may not exceed it - so not every hit breaks the wall.

 

[Dausuul]

IMO, all of your problems are coming from the decision to give only 27 hit points per panel to the stone wall.

I know that is what the DMG suggests for a 10x10 "resilient" object, but I strongly urge you to consider that as a minimum rather than a universal rule. It's absurd to suppose that a 10x10 panel of wooden boards and a 10x10x10 cube of adamantine should have the same number of hit points, making them equally vulnerable to any attack that doesn't target AC.

Compare to the wall of stone spell: Each 10x10 panel has 180* hit points! Now that is more in line with what I would expect from a solid stone wall. And as a general principle, I feel that a stone wall built by the labor of skilled masons should be at least equal to a stone wall conjured up by the wave of a wizard's hand.

If you up the wall's hit points to 180, it all works a lot better. The dragon's breath is still dangerous to the wall, but one blast is not sufficient to make it collapse. It takes three blasts to the same 10x10 panel, which requires ~7 rounds: 1 round for the first blast, 3 rounds to recharge for the second blast, 3 rounds to recharge for the third. That gives the PCs time to react while the dragon is (literally) focusing fire.

*Assuming you go with the default thickness of 6 inches.

 

[jgsugden]

I would look to the last season of Game of Thrones for inspiration for how Dragon Breath can interact with stone.

Spoiler

(Check out 2:20 or so in....)

Historically, if the dragon breath can destroy something, I have it obliterate it and pass through on to other things as if the obstruction was not there. However, there is some wiggle room for situations like multiple layers of walls where I may consider them to be treated as multiple layers of the same wall, effectively increasing their hps.

The same is true of spells that can damage objects. This does not apply to poison gas clouds, but does to fire, cold, lightning, thunder, acid, etc... An ancient red dragon breath of a 90' cone can obliterate entire buildings.

 

[the Jester]

I personally think 2d10 for natural lightning is incredibly low. In an area of poor conductivity lightning can get 5 times hotter than the surface of the sun. I would put it closer to 10d10 with a dexterity save.

In 1e's Wilderness Survival Guide, if you got hit by natural lightning, it did 1d20 dice of damage. That's right, anywhere from 1d6 to 20d6, at random.

 

[Chaosmancer]

I would look to the last season of Game of Thrones for inspiration for how Dragon Breath can interact with stone.

Spoiler

MEDIA=youtube]xTvtQSSRuVs[/MEDIA] (Check out 2:20 or so in....)

Historically, if the dragon breath can destroy something, I have it obliterate it and pass through on to other things as if the obstruction was not there. However, there is some wiggle room for situations like multiple layers of walls where I may consider them to be treated as multiple layers of the same wall, effectively increasing their hps.

The same is true of spells that can damage objects. This does not apply to poison gas clouds, but does to fire, cold, lightning, thunder, acid, etc... An ancient red dragon breath of a 90' cone can obliterate entire buildings.

You link didn't copy properly.

IMO, all of your problems are coming from the decision to give only 27 hit points per panel to the stone wall.

I know that is what the DMG suggests for a 10x10 "resilient" object, but I strongly urge you to consider that as a minimum rather than a universal rule. It's absurd to suppose that a 10x10 panel of wooden boards and a 10x10x10 cube of adamantine should have the same number of hit points, making them equally vulnerable to any attack that doesn't target AC.

Compare to the wall of stone spell: Each 10x10 panel has 180* hit points! Now that is more in line with what I would expect from a solid stone wall. And as a general principle, I feel that a stone wall built by the labor of skilled masons should be at least equal to a stone wall conjured up by the wave of a wizard's hand.

If you up the wall's hit points to 180, it all works a lot better. The dragon's breath is still dangerous to the wall, but one blast is not sufficient to make it collapse. It takes three blasts to the same 10x10 panel, which requires ~7 rounds: 1 round for the first blast, 3 rounds to recharge for the second blast, 3 rounds to recharge for the third. That gives the PCs time to react while the dragon is (literally) focusing fire.

*Assuming you go with the default thickness of 6 inches.

Hmm, I hadn't looked closely at that spell in a while. But, that also got me looking at Wall of Ice, and I would have to submit that one of those two numbers is wrong, and I feel it is the wall of stone.

Wall of stone is 30 hp per 1 inch of stone

Wall of Ice is 30hp per 1 foot of ice.

Now, I've had to break a few inches of ice before. It is tough stuff. I can imagine if I had a block of ice 1 foot thick, and I hit it with a sledgehammer (equivalent to a maul) I probably would not split it in half. I'd take a chunk out, but not destroy it.

An inch thin sheet of stone? Broken, I would be shocked if it could stand up to more than a single hammer blow.

And a maul does an average of 7 damage. So, would we really expect it to take 5 hammer blows to break an inch of stone? My gut says no.

So either the stone from Wall of Stone is unusual, or it needs to be weakened, because I don't think those numbers work out very well on the base line.

 

[Oofta]

There are some things the rules just don't handle well. In theory, someone could chisel their way through a solid stone wall with a dagger in a few hours. In reality you wouldn't do much more than scratch the surface.

I understand that dragon breath is hot but it would have to be so hot that it would incinerate anyone in it's path immediately in order to make a significant difference. It doesn't do that so personally I'd just ignore what the rules say and use common sense.

 

[Eyes of Nine]

Just send in the white dragon to freeze the section of the wall, THEN have the red dragon flame it. Instant shatter.

Which is to say, the rules are not great about this.

 

[dave2008]

There are some things the rules just don't handle well. In theory, someone could chisel their way through a solid stone wall with a dagger in a few hours. In reality you wouldn't do much more than scratch the surface.

Well that is dependent on a lot of things. I just watched the most recent episode of "This Old House" and they did in fact use hand tools to chip out an approximately 18" thick by 24" high by 48" wide section of a stone foundation. It didn't appear to take very long (hard to tell though), but they attacked the joints and then pulled the stones out.

 

[Oofta]

Well that is dependent on a lot of things. I just watched the most recent episode of "This Old House" and they did in fact use hand tools to chip out an approximately 18" thick by 24" high by 48" wide section of a stone foundation. It didn't appear to take very long (hard to tell though), but they attacked the joints and then pulled the stones out.

They were chipping out mortar, not stone. Old mortar can be easy to chip out but I also wouldn't be surprised if they were using a hammer and chisel.

I mean, go ahead. Go out somewhere and find a nice chunk of granite. Try to carve through it with a jack-knife and see how far you get. Heck, use a hardened chisel with no hammer. It's something you could do following the letter of the rules in D&D but in real life you'd break your knife first.

There's a reason that trebuchets threw rocks that weighed at least a couple hundred pounds. Even then, it took constant bombardment over days if not weeks to take down walls.

 

[dave2008]

They were chipping out mortar, not stone. Old mortar can be easy to chip out but I also wouldn't be surprised if they were using a hammer and chisel.

I mean, go ahead. Go out somewhere and find a nice chunk of granite. Try to carve through it with a jack-knife and see how far you get. Heck, use a hardened chisel with no hammer. It's something you could do following the letter of the rules in D&D but in real life you'd break your knife first.

There's a reason that trebuchets threw rocks that weighed at least a couple hundred pounds. Even then, it took constant bombardment over days if not weeks to take down walls.

Like I said there are a lot of variables. In TOH they did in fact attack the mortar. I remember them using a hand-held pick-axe, a crowbar and something else (just can't remember what). This technique wouldn't really work for an exterior castle wall, but it could be effective for some other types of stone walls.

FYI, I have done quite a bit of concrete work and some masonry work in my time and have or had most of the tools needed to work stone by hand. The type of stone makes a big difference too.

Also, did you know it is possible for a human to run through a single-wythe brick wall and for concrete to explode from to much heat.