Sorry if I'm a bit fashionably late to the party--I was wondering if the damage triggered when the target of Booming Blade moves more than 5 feet gets doubled on a critical hit, and my search for an answer brought me to this thread.
I appreciate all the points and counter-points brought up in this discussion, so thank you to all who have contributed! On a lark, I decided to find out WWDNDBD (What Would DnDBeyond Do?) and did a little testing, and found out that when damage is rolled after scoring a critical hit with your melee weapon as part of casting Booming Blade, DnDBeyond does, in fact, roll critical damage dice for both the Thunder Damage inflicted with the initial hit as well as the extra Thunder Damage inflicted by the target's movement.
Anyway, I'm not sure if that helps at all, but I did want to share my findings on the matter. :)
Sorry if I'm a bit fashionably late to the party--I was wondering if the damage triggered when the target of Booming Blade moves more than 5 feet gets doubled on a critical hit, and my search for an answer brought me to this thread.
I appreciate all the points and counter-points brought up in this discussion, so thank you to all who have contributed! On a lark, I decided to find out WWDNDBD (What Would DnDBeyond Do?) and did a little testing, and found out that when damage is rolled after scoring a critical hit with your melee weapon as part of casting Booming Blade, DnDBeyond does, in fact, roll critical damage dice for both the Thunder Damage inflicted with the initial hit as well as the extra Thunder Damage inflicted by the target's movement.
Anyway, I'm not sure if that helps at all, but I did want to share my findings on the matter. :)
If you could walk is through your test procedure and share a link to the character you tested it on I would appreciate it.
However I was not able to reproduce your results. I rolled attacks with my Greataxe until I rolled a natural 20. I then checked my Greataxe damage and confirmed that it was doubled to 2d12 and everything else was still normal. Then I clicked over to the Spells tab and looked at the Booming Blade damage and it was listed as 1d8. When I clicked back over to the Actions tab my Greataxe damage had returned to 1d12.
From this I have a few observations about DnDBeyond's functionality. First, a critical hit is correctly associated with the attack that rolled it. Second, it seems like clicking over to another tab in the DnDBeyond character sheet will clear the critical hit from memory, even if damage was never rolled. Third, the damage shown in the Spells tab is for the on hit damage, not the proc damage if the creature moves.
So to me it seems like DnDBeyond can't even correctly double the on hit damage of Booming Blade. This is why I would like to know how you tested it.
Sorry if I'm a bit fashionably late to the party--I was wondering if the damage triggered when the target of Booming Blade moves more than 5 feet gets doubled on a critical hit, and my search for an answer brought me to this thread.
I appreciate all the points and counter-points brought up in this discussion, so thank you to all who have contributed! On a lark, I decided to find out WWDNDBD (What Would DnDBeyond Do?) and did a little testing, and found out that when damage is rolled after scoring a critical hit with your melee weapon as part of casting Booming Blade, DnDBeyond does, in fact, roll critical damage dice for both the Thunder Damage inflicted with the initial hit as well as the extra Thunder Damage inflicted by the target's movement.
Anyway, I'm not sure if that helps at all, but I did want to share my findings on the matter. :)
If you could walk is through your test procedure and share a link to the character you tested it on I would appreciate it.
However I was not able to reproduce your results. I rolled attacks with my Greataxe until I rolled a natural 20. I then checked my Greataxe damage and confirmed that it was doubled to 2d12 and everything else was still normal. Then I clicked over to the Spells tab and looked at the Booming Blade damage and it was listed as 1d8. When I clicked back over to the Actions tab my Greataxe damage had returned to 1d12.
From this I have a few observations about DnDBeyond's functionality. First, a critical hit is correctly associated with the attack that rolled it. Second, it seems like clicking over to another tab in the DnDBeyond character sheet will clear the critical hit from memory, even if damage was never rolled. Third, the damage shown in the Spells tab is for the on hit damage, not the proc damage if the creature moves.
So to me it seems like DnDBeyond can't even correctly double the on hit damage of Booming Blade. This is why I would like to know how you tested it.
Absolutely, here is the method I used. I'm providing pictures of each step for clarity, because--as you said--clicking over into different parts of the character sheet can interfere with the way DnDBeyond "remembers" critical hits. Also, as a note, I was using the Beyond20 extension in my browser (which is Firefox, but this also works the same way with the Beyond20 extension for Google Chrome) as the group I play with online uses Roll20.net as our Virtual Table Top, so this is exactly how it would play out in an actual game using that setup.
Lord Bergamot is wielding a Holy Avenger Greatsword in this example, but really, that's irrelevant for the purposes of this demonstration--any melee weapon will work, following the steps below:
1. From the ACTIONS tab on your character sheet, click on the melee weapon that you wish you use with the Booming Blade cantrip. A window will open to the right, featuring the stats and description of the weapon, along with a clickable red BEYOND20 button that you can click to initiate the attack roll required with the casting of the cantrip.
Just for the sake of full disclosure, I am showing here that I have activated the Great Weapon Master feat's -5 to the attack roll/+10 to damage option, as well as the Hexblade's Curse option that results in a critical hit on a roll of 19 or 20 (to make it easier to get the attack roll needed to activate DnDBeyond's rolling of critical damage dice):
2. After several rolls, I finally roll a 19, which counts as a critical hit with Hexblade's Curse active. The resulting attack roll is sent over to the Virtual Table Top at Roll20.net.
3. Over on the VTT, clicking the name of the weapon where it is highlighted in pink causes all of the information about the attack roll that was sent over from DnDBeyond to be parsed, and all of the requisite damage rolls take place automatically. The results of all damage rolled is neatly laid out and separated for us, and we can see that there are 2 boxes at the very end (just before the final totals section), both titled "Thunder (Booming Blade) Critical Damage".
4. If we hover the mouse over the first of these, we can see amongst all the parse data for that specific roll that the 7 is the total for the 3d8 rolled as the critical Thunder Damage inflicted with the attack roll hit (from a 2+1+4)...
5. ...while hovering over the 23 in the second field shows us that the total there is from a roll of 4d8, which would be rolled as the additional critical Thunder Damage inflicted by the Booming Blade target's movement (from the total of 4+8+7+4).
Hopefully that all helps with being able to reproduce my results :)
EDIT/ADDENDUM #1: I was able to reproduce this from the Barbarian/Wizard's character sheet you linked above, using Booming Blade in tandem with his Greataxe. The formatting of the results ended up looking a bit different (I don't know if that's because I'm not the owner of that character, so the information sent from DnDBeyond was processed differently, maybe?), but here's what that looked like:
EDIT/ADDENDUM #2: For the sake of being thorough, I went back and repeated the test again, this time equipping Lord Bergamont with a normal Greataxe, so that he is using the same weapon as you have equipped on your Barbarian/Wizard. In this test, I also did not activate any extra features (so no Great Weapon Master feat effect, and no Hexblade's Curse), and just utilized a straight roll of a natural 20 to determine a critical hit with the methodology I described in the steps above:
...and this is the result of the damage rolls parsed in the Roll20.net VTT, which again shows the rolls of both a 3d8 and 4d8 for the Booming Blade critical hit thunder damage.
I'd also argue that not only isn't it D&DB, it isn't doing any rule interpretation; it is dumbly doubling whatever D&DB provides to it as "damage" for that attack.
I'd also argue that not only isn't it D&DB, it isn't doing any rule interpretation; it is dumbly doubling whatever D&DB provides to it as "damage" for that attack.
I'd concede the possibility of that, except for the fact that it is separating out critical damage rolls from the non-critical damage rolls, and actually rolling those dice separately, not merely multiplying the number by 2 or doubling the number of dice rolled and lumping it all together. In addition, in the initial example I provided, the damage caused by Hexblade's Curse and the damage inflicted by the Great Weapon Master feat are not being multiplied--there is only one instance of each of those damages listed, it's not applying "critical damage" for those, which demonstrates that (IMO) specific damages are being flagged as qualifying to be applied as additional critical damage, while others are not.
This certainly could be due to DnDBeyond having flagged the information re: the Thunder Damage rolls that is being passed to Roll20 (via the Beyond20 extension) as being eligible for critical damage rolls. Then again, as you suggested, it might be the Beyond20 extension doing it. I don't know for sure.
What I do know that is that it is rolling both the Thunder Damage for the initial critical hit and the Thunder Damage caused by the target moving as additional critical damage, and both are separate rolls for critical damage (not all just one lump sum). As to whether that's in error, or whether that's being done correctly--that I do not know. But that's the whole point of the discussion in this thread... I'm just pointing out how the system is calculating it via the setup for online play that our group uses, which is a system used by many people.
What I do know that is that it is rolling both the Thunder Damage for the initial critical hit and the Thunder Damage caused by the target moving as additional critical damage, and both are separate rolls for critical damage (not all just one lump sum). As to whether that's in error, or whether that's being done correctly--that I do not know. But that's the whole point of the discussion in this thread... I'm just pointing out how the system is calculating it via the setup for online play that our group uses, which is a system used by many people.
It's definitely in error; the additional damage for moving is not part of the attack, it's a separate effect that applies later. Most likely it's a bug with Beyond20 and the fact that the secondary damage is listed alongside the initial damage.
Avrae (Discord dice roller) for example doesn't try to roll these at all, you can either separately cast the cantrip to roll the initial damage (then roll the secondary damage yourself separately iirc) or you have to add a snippet that adds the extra damage automatically. Since this a semi-official tool of D&D Beyond I think we can assume that there's no way to pull the information out of a sheet correctly or they'd be doing that, so Beyond20 either shouldn't be trying to do it, or needs to add special handling for these cantrips.
I think you're making a lot of assumptions that are different from mine. I assume that the other app is dumbly doubling damage in a way remotely consistent with the rules: doubling the number of dice being sent in as "damage dice," not just 2*total.
The problem is that the interface between these apps doesn't make the correct assumptions. Apparently Beyond20 or whatever doesn't realize that all of the dice being sent as 'the spell' are not part of the attack like they might be for a smite or something else.
I haven't read through your post KnightFyre but thank you for going over your procedure in such detail!
I just wanted to add quickly that the reason I made a Wizard/Barbarian to test this is I wanted to see if it would also work with one of the natural weapons provided by the Path of the Beast when raging. These are two game elements that should never actually interact and that is why I wanted to test it and other impossible combinations.
I haven't read through your post KnightFyre but thank you for going over your procedure in such detail!
I just wanted to add quickly that the reason I made a Wizard/Barbarian to test this is I wanted to see if it would also work with one of the natural weapons provided by the Path of the Beast when raging. These are two game elements that should never actually interact and that is why I wanted to test it and other impossible combinations.
Ahh, that does not seem to work--when clicking on the Form of the Beast: Bite/Claws/Tail attacks, there is no associated Booming Blade section listed as being available for those weapons (as there is for the greataxe).
So, in a bit of further testing, I closed the Roll20 VTT tab and CTRL-F5 refreshed the tab that I had opened to Lord Bergamont's character sheet on DnDBeyond, so DnDBeyond was the only website opened in the browser.
I followed the same procedures above, except that after rolling the Booming Blade melee attack with the greataxe, since there was no Virtual Table Top detected, the only option was to roll the damage right there in DnDBeyond, as depicted below:
...after clicking the Roll Damages button in the pop-up that appeared after the natural 20 critical hit is rolled for the Booming Blade melee attack, the damage dice were rolled, and this is the result--again, as shown in DnDBeyond:
As we can see, in this case where the VTT has been completely cut out of the equation and we're dealing strictly with the DnDBeyond site, on a critical hit it is still rolling 3d8 for the Critical Thunder Damage inflicted by the initial melee attack, and it is also still rolling the 4d8 for the Critical Thunder Damage which is inflicted if the target moves (in addition to all the normal damages that would regularly be rolled).
I have read through it and I had a question. It looks like the 3d8 on hit damage was rolled at the same time as the 4d8 on move damage, is this correct?
Because if so that is itself a bug as the on move damage shouldn't be rolled until the creature willingly moves 5ft.
I am not familiar with Beyond20 and Roll20 so I would hesitate to say where this bug is. But if it is with Beyond20 then it at least seems to be open source, I found its GitHub repo when looking it up: https://github.com/kakaroto/Beyond20
Edit: Roll20 has been proven innocent thanks to Knightfyre!
So I haven't thoroughly explored the code, but from what I've seen, it looks like beyond 20 specially parses some spells like blade of disaster, but as I implied, dumbly applies the same rules to everything else. This should be considered a bug.
Edit: special rules for a couple of spells implemented with special crit rules in the Beyond20 code (beyond20/src/dndbeyond/base/utils.js).
if (roll_properties.name === "Blade of Disaster") crit_damages[0] = damagesToCrits(character, ["8d12"])[0]; if (roll_properties.name === "Jim’s Magic Missile") crit_damages[0] = damagesToCrits(character, ["3d4"])[0];
I have read through it and I had a question. It looks like the 3d8 on hit damage was rolled at the same time as the 4d8 on move damage, is this correct?
Because if so that is itself a bug as the on move damage shouldn't be rolled until the creature willingly moves 5ft.
I am not familiar with Beyond20 and Roll20 so I would hesitate to say where this bug is. But if it is with Beyond20 then it at least seems to be open source, I found its GitHub repo when looking it up: https://github.com/kakaroto/Beyond20
Edit: Roll20 has been proven innocent thanks to Knightfyre
Yes, that is correct--it does roll both the 3d8 on-hit damage and the 4d8 on-move damage at the same time, but it does separate them into unique totals.
In a bit of further testing, I applied the same methodology to the Green-Flame Blade cantrip, and discovered that on a critical hit, it rolls critical damage for both the target struck by the attack, as well as for the adjacent target that is struck by the splash damage. This we know for certain should not be happening, as Jeremy Crawford succinctly clarified, "the splash damage of Green-Flame Blade isn't affected by the attack critting." In light of that, the fact that the system is rolling critical thunder damage for both the initial melee attack's critical hit as well as the target's subsequent movement is not reliable evidence that this is the way Booming Blade is intended to work, and as Haravikk and WolfOfTheBees have suggested, is very possibly a bug.
Yes, that is correct--it does roll both the 3d8 on-hit damage and the 4d8 on-move damage at the same time, but it does separate them into unique totals.
In a bit of further testing, I applied the same methodology to the Green-Flame Blade cantrip, and discovered that on a critical hit, it rolls critical damage for both the target struck by the attack, as well as for the adjacent target that is struck by the splash damage. This we know for certain should not be happening, as Jeremy Crawford succinctly clarified, "the splash damage of Green-Flame Blade isn't affected by the attack critting." In light of that, the fact that the system is rolling critical thunder damage for both the initial melee attack's critical hit as well as the target's subsequent movement is not reliable evidence that this is the way Booming Blade is intended to work, and as Haravikk and WolfOfTheBees have suggested, is very possibly a bug.
Jeremy Crawford's rulings aren't RAW, but the RAW on both BB and GFB is clear (well, mostly - see below) - in both cases the "secondary" damage is not based on an attack roll and so of course can't crit. If DDB is doubling them on a crit, that's simply a bug, which you should report in the bugs forum.
You never apply crit damage to a damage effect where you didn't roll an attack roll as a prerequisite to rolling the damage, even if the effect needed an attack roll to get started. For example, Alchemist's Fire can't achieve crit damage, and neither can recurring poisons, even if the original delivery of the ongoing fire or poison damage effect was an attack roll that critted. Likewise, if you're fighting a bearded devil, the recurring wound damage doesn't care if the devil critted when it wounded you. The same rule applies everywhere in the game, and you have to be explicitly told when it stops applying. Because neither BB nor GFB cause simultaneous damage - the secondary damage happens after the initial damage - both are subject to this rule.
That's another easy way to tell DDB is being buggy: because the damage is sequential and not simul, DDB is violating the game rules by rolling them at the same time in ways that can matter. For example, if you have access to any of a number of game rules that will let you add a modifier to any one damage roll of a damaging spell, you have to decide, for both spells, if you're applying the modifier to the first damage roll before you even see the second damage roll. DDB is essentially cheating in your favor by showing you both damage results before the first has actually occurred.
If DDB is doubling them on a crit, that's simply a bug, which you should report in the bugs forum.
Just a small clarification, it isn't DnDBeyond that has the bug, but rather the plug-in Beyond20.
Yeah, what Knightfyre's screenshots are showing are not the normal behaviour for D&D Beyond's dice roller; the D&D Beyond dice roller only lets us roll basic weapon damage, or double the dice for a critical hit, everything else we need to add manually using the custom roller option (in the bottom left) or some other tool.
It looks like Beyond20 might be trying to automatically roll what it thinks is added weapon damage, but it's just looking at the description for the weapon and seeing 2d8 + 3d8 and adding it all on top without accounting for the source of each damage type. Basically it's treating it as if it were a magic weapon with added damage on all attacks, because it's not aware that the 3d8 in this case is secondary damage with its own conditions.
Sorry if I'm a bit fashionably late to the party--I was wondering if the damage triggered when the target of Booming Blade moves more than 5 feet gets doubled on a critical hit, and my search for an answer brought me to this thread.
I appreciate all the points and counter-points brought up in this discussion, so thank you to all who have contributed! On a lark, I decided to find out WWDNDBD (What Would DnDBeyond Do?) and did a little testing, and found out that when damage is rolled after scoring a critical hit with your melee weapon as part of casting Booming Blade, DnDBeyond does, in fact, roll critical damage dice for both the Thunder Damage inflicted with the initial hit as well as the extra Thunder Damage inflicted by the target's movement.
Anyway, I'm not sure if that helps at all, but I did want to share my findings on the matter. :)
If you could walk is through your test procedure and share a link to the character you tested it on I would appreciate it.
I tried testing this myself on this character: https://ddb.ac/characters/83389070/NAAvuE
However I was not able to reproduce your results. I rolled attacks with my Greataxe until I rolled a natural 20. I then checked my Greataxe damage and confirmed that it was doubled to 2d12 and everything else was still normal. Then I clicked over to the Spells tab and looked at the Booming Blade damage and it was listed as 1d8. When I clicked back over to the Actions tab my Greataxe damage had returned to 1d12.
From this I have a few observations about DnDBeyond's functionality. First, a critical hit is correctly associated with the attack that rolled it. Second, it seems like clicking over to another tab in the DnDBeyond character sheet will clear the critical hit from memory, even if damage was never rolled. Third, the damage shown in the Spells tab is for the on hit damage, not the proc damage if the creature moves.
So to me it seems like DnDBeyond can't even correctly double the on hit damage of Booming Blade. This is why I would like to know how you tested it.
Absolutely, here is the method I used. I'm providing pictures of each step for clarity, because--as you said--clicking over into different parts of the character sheet can interfere with the way DnDBeyond "remembers" critical hits. Also, as a note, I was using the Beyond20 extension in my browser (which is Firefox, but this also works the same way with the Beyond20 extension for Google Chrome) as the group I play with online uses Roll20.net as our Virtual Table Top, so this is exactly how it would play out in an actual game using that setup.
First, the character I used: Lord Bergamot is pleased to make your acquaintance! https://www.dndbeyond.com/characters/83645622
Lord Bergamot is wielding a Holy Avenger Greatsword in this example, but really, that's irrelevant for the purposes of this demonstration--any melee weapon will work, following the steps below:
1. From the ACTIONS tab on your character sheet, click on the melee weapon that you wish you use with the Booming Blade cantrip. A window will open to the right, featuring the stats and description of the weapon, along with a clickable red BEYOND20 button that you can click to initiate the attack roll required with the casting of the cantrip.
Just for the sake of full disclosure, I am showing here that I have activated the Great Weapon Master feat's -5 to the attack roll/+10 to damage option, as well as the Hexblade's Curse option that results in a critical hit on a roll of 19 or 20 (to make it easier to get the attack roll needed to activate DnDBeyond's rolling of critical damage dice):
2. After several rolls, I finally roll a 19, which counts as a critical hit with Hexblade's Curse active. The resulting attack roll is sent over to the Virtual Table Top at Roll20.net.
3. Over on the VTT, clicking the name of the weapon where it is highlighted in pink causes all of the information about the attack roll that was sent over from DnDBeyond to be parsed, and all of the requisite damage rolls take place automatically. The results of all damage rolled is neatly laid out and separated for us, and we can see that there are 2 boxes at the very end (just before the final totals section), both titled "Thunder (Booming Blade) Critical Damage".
4. If we hover the mouse over the first of these, we can see amongst all the parse data for that specific roll that the 7 is the total for the 3d8 rolled as the critical Thunder Damage inflicted with the attack roll hit (from a 2+1+4)...
5. ...while hovering over the 23 in the second field shows us that the total there is from a roll of 4d8, which would be rolled as the additional critical Thunder Damage inflicted by the Booming Blade target's movement (from the total of 4+8+7+4).
Hopefully that all helps with being able to reproduce my results :)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
EDIT/ADDENDUM #1:
I was able to reproduce this from the Barbarian/Wizard's character sheet you linked above, using Booming Blade in tandem with his Greataxe. The formatting of the results ended up looking a bit different (I don't know if that's because I'm not the owner of that character, so the information sent from DnDBeyond was processed differently, maybe?), but here's what that looked like:
EDIT/ADDENDUM #2:
For the sake of being thorough, I went back and repeated the test again, this time equipping Lord Bergamont with a normal Greataxe, so that he is using the same weapon as you have equipped on your Barbarian/Wizard. In this test, I also did not activate any extra features (so no Great Weapon Master feat effect, and no Hexblade's Curse), and just utilized a straight roll of a natural 20 to determine a critical hit with the methodology I described in the steps above:
...and this is the result of the damage rolls parsed in the Roll20.net VTT, which again shows the rolls of both a 3d8 and 4d8 for the Booming Blade critical hit thunder damage.
That's Beyond20 doing that, not DDB.
Helpful rewriter of Japanese->English translation and delver into software codebases (she/e/they)
I'd also argue that not only isn't it D&DB, it isn't doing any rule interpretation; it is dumbly doubling whatever D&DB provides to it as "damage" for that attack.
Edit: "damage dice" rather than "damage."
I'd concede the possibility of that, except for the fact that it is separating out critical damage rolls from the non-critical damage rolls, and actually rolling those dice separately, not merely multiplying the number by 2 or doubling the number of dice rolled and lumping it all together. In addition, in the initial example I provided, the damage caused by Hexblade's Curse and the damage inflicted by the Great Weapon Master feat are not being multiplied--there is only one instance of each of those damages listed, it's not applying "critical damage" for those, which demonstrates that (IMO) specific damages are being flagged as qualifying to be applied as additional critical damage, while others are not.
This certainly could be due to DnDBeyond having flagged the information re: the Thunder Damage rolls that is being passed to Roll20 (via the Beyond20 extension) as being eligible for critical damage rolls. Then again, as you suggested, it might be the Beyond20 extension doing it. I don't know for sure.
What I do know that is that it is rolling both the Thunder Damage for the initial critical hit and the Thunder Damage caused by the target moving as additional critical damage, and both are separate rolls for critical damage (not all just one lump sum). As to whether that's in error, or whether that's being done correctly--that I do not know. But that's the whole point of the discussion in this thread... I'm just pointing out how the system is calculating it via the setup for online play that our group uses, which is a system used by many people.
It's definitely in error; the additional damage for moving is not part of the attack, it's a separate effect that applies later. Most likely it's a bug with Beyond20 and the fact that the secondary damage is listed alongside the initial damage.
Avrae (Discord dice roller) for example doesn't try to roll these at all, you can either separately cast the cantrip to roll the initial damage (then roll the secondary damage yourself separately iirc) or you have to add a snippet that adds the extra damage automatically. Since this a semi-official tool of D&D Beyond I think we can assume that there's no way to pull the information out of a sheet correctly or they'd be doing that, so Beyond20 either shouldn't be trying to do it, or needs to add special handling for these cantrips.
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I think you're making a lot of assumptions that are different from mine. I assume that the other app is dumbly doubling damage in a way remotely consistent with the rules: doubling the number of dice being sent in as "damage dice," not just 2*total.
The problem is that the interface between these apps doesn't make the correct assumptions. Apparently Beyond20 or whatever doesn't realize that all of the dice being sent as 'the spell' are not part of the attack like they might be for a smite or something else.
I haven't read through your post KnightFyre but thank you for going over your procedure in such detail!
I just wanted to add quickly that the reason I made a Wizard/Barbarian to test this is I wanted to see if it would also work with one of the natural weapons provided by the Path of the Beast when raging. These are two game elements that should never actually interact and that is why I wanted to test it and other impossible combinations.
Ahh, that does not seem to work--when clicking on the Form of the Beast: Bite/Claws/Tail attacks, there is no associated Booming Blade section listed as being available for those weapons (as there is for the greataxe).
So, in a bit of further testing, I closed the Roll20 VTT tab and CTRL-F5 refreshed the tab that I had opened to Lord Bergamont's character sheet on DnDBeyond, so DnDBeyond was the only website opened in the browser.
I followed the same procedures above, except that after rolling the Booming Blade melee attack with the greataxe, since there was no Virtual Table Top detected, the only option was to roll the damage right there in DnDBeyond, as depicted below:
...after clicking the Roll Damages button in the pop-up that appeared after the natural 20 critical hit is rolled for the Booming Blade melee attack, the damage dice were rolled, and this is the result--again, as shown in DnDBeyond:
As we can see, in this case where the VTT has been completely cut out of the equation and we're dealing strictly with the DnDBeyond site, on a critical hit it is still rolling 3d8 for the Critical Thunder Damage inflicted by the initial melee attack, and it is also still rolling the 4d8 for the Critical Thunder Damage which is inflicted if the target moves (in addition to all the normal damages that would regularly be rolled).
I have read through it and I had a question. It looks like the 3d8 on hit damage was rolled at the same time as the 4d8 on move damage, is this correct?
Because if so that is itself a bug as the on move damage shouldn't be rolled until the creature willingly moves 5ft.
I am not familiar with Beyond20 and Roll20 so I would hesitate to say where this bug is. But if it is with Beyond20 then it at least seems to be open source, I found its GitHub repo when looking it up: https://github.com/kakaroto/Beyond20
Edit: Roll20 has been proven innocent thanks to Knightfyre!
So I haven't thoroughly explored the code, but from what I've seen, it looks like beyond 20 specially parses some spells like blade of disaster, but as I implied, dumbly applies the same rules to everything else. This should be considered a bug.
Edit: special rules for a couple of spells implemented with special crit rules in the Beyond20 code (beyond20/src/dndbeyond/base/utils.js).
Yes, that is correct--it does roll both the 3d8 on-hit damage and the 4d8 on-move damage at the same time, but it does separate them into unique totals.
In a bit of further testing, I applied the same methodology to the Green-Flame Blade cantrip, and discovered that on a critical hit, it rolls critical damage for both the target struck by the attack, as well as for the adjacent target that is struck by the splash damage. This we know for certain should not be happening, as Jeremy Crawford succinctly clarified, "the splash damage of Green-Flame Blade isn't affected by the attack critting." In light of that, the fact that the system is rolling critical thunder damage for both the initial melee attack's critical hit as well as the target's subsequent movement is not reliable evidence that this is the way Booming Blade is intended to work, and as Haravikk and WolfOfTheBees have suggested, is very possibly a bug.
Jeremy Crawford's rulings aren't RAW, but the RAW on both BB and GFB is clear (well, mostly - see below) - in both cases the "secondary" damage is not based on an attack roll and so of course can't crit. If DDB is doubling them on a crit, that's simply a bug, which you should report in the bugs forum.
You never apply crit damage to a damage effect where you didn't roll an attack roll as a prerequisite to rolling the damage, even if the effect needed an attack roll to get started. For example, Alchemist's Fire can't achieve crit damage, and neither can recurring poisons, even if the original delivery of the ongoing fire or poison damage effect was an attack roll that critted. Likewise, if you're fighting a bearded devil, the recurring wound damage doesn't care if the devil critted when it wounded you. The same rule applies everywhere in the game, and you have to be explicitly told when it stops applying. Because neither BB nor GFB cause simultaneous damage - the secondary damage happens after the initial damage - both are subject to this rule.
That's another easy way to tell DDB is being buggy: because the damage is sequential and not simul, DDB is violating the game rules by rolling them at the same time in ways that can matter. For example, if you have access to any of a number of game rules that will let you add a modifier to any one damage roll of a damaging spell, you have to decide, for both spells, if you're applying the modifier to the first damage roll before you even see the second damage roll. DDB is essentially cheating in your favor by showing you both damage results before the first has actually occurred.
Just a small clarification, it isn't DnDBeyond that has the bug, but rather the plug-in Beyond20.
Yeah, what Knightfyre's screenshots are showing are not the normal behaviour for D&D Beyond's dice roller; the D&D Beyond dice roller only lets us roll basic weapon damage, or double the dice for a critical hit, everything else we need to add manually using the custom roller option (in the bottom left) or some other tool.
It looks like Beyond20 might be trying to automatically roll what it thinks is added weapon damage, but it's just looking at the description for the weapon and seeing 2d8 + 3d8 and adding it all on top without accounting for the source of each damage type. Basically it's treating it as if it were a magic weapon with added damage on all attacks, because it's not aware that the 3d8 in this case is secondary damage with its own conditions.
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