Wasn't sure where to post this, so I went for General Discussion.
So I've been playing around building new PCs with backstory and fun quirks to put in my library. Recently I got onto a speed kick with monk builds but when looking around the boards, most discussions are about utilizing EVERY possible action, extra action, bonus action, etc. for going faster. I, personally, struggle to think of the practical application for that in battle, and it's very niche outside of battle as well. So a practical application of ludicrous speed would be to utilize said speed kinetically.
So, I guess my question is what do y'all think would be the best way to calculate mass bludgeoning damage?
If I multiclass druid of the moon and fly very high in the sky as a giant eagle and then hit "diving speed" as I plunged towards the BBEG, my rough estimate with feats, haste, and boots of speed would be close to 180 mph, WITHOUT using my bonus action. If i then, right before colliding with the BBEG, bonus action transformed into a Huge sized creature like an elephant or a whale... how would you calculate that damage as a DM??
I would start with falling damage, for starters. For each 10 feet you fall, you take 1d6 damage to a maximum of 20d6 at 200 ft. Newton's third law tells us that if you take that damage, whatever you impact should take equal damage. As a DM I'd probably stop right there, and maybe impose disadvantage on a Dexterity saving throw to avoid being crushed due tot he speed and size increase. But we can go further for fun.
For turning into a larger creature, there's no RAW that makes this official, but looking through some other options can help. Animate Objects gives us a clue about how much damage can be done by objects. A huge animated object deals 2d12 + 4 damage on a hit. One could treat dropping such an object as an attack. I would sooner double the damage and call for a saving throw for half, ie. being crushed by a Huge object deals 4d12 + 8 damage or half on a successful Dexterity saving throw. A collapsing roof trap (from the DMG) deals 4d10 damage or half on a successful Dexterity saving throw, which gives us another clue.
Now as for velocity, that's tricky. An object falling without any added force is assumed to fall at a rate of 500 ft/round (from XGtE). Supposing the Monk adds 180 ft. to that movement speed, it would add just over 1/3 to the velocity of the object. If you want to be super precise, you could take the 1d6 damage per 10 ft. above and change the damage scale to reflect this increase. For instance, 20d6 gives an average damage of 70, but you could increase the die to a d8 per 10 ft. giving us a total of 20d8 damage, which gives an average of 90 damage. That's an increase of under 30%, but it's close enough IMO. A d10 would drive up the average damage by over 50%, which is probably too much.
In principle, the average impact force is given by the equation F = (mv^2)/2d, m being mass, v being velocity, and d being impact distance (eg. about 2 meters of impact to flatten a relatively tall human). This implies that mass and the square of velocity should figure together multiplicatively. That dramatically alters the math, but this is already wayyy more pedantic than you want to be at your table.
Edit: Might as well go the full way. Suppose the falling damage we get from the DMG is given as a proportion of impact force.
20d6 ~ (mv^2)/2d
and we assume that an average Medium creature weighs 65 kg, and has a height of 2m. Then suppose you increase the velocity of the fall by 1/3, and increase the mass by a factor of ~70 (assuming you become an average African elephant at ~4500 kg). Then the damage you inflict on a 2 meter creature on the ground should increase by %dM + 2*%dv ~ 70.00 + 2*.33 ~ 70.66 or 7066% (the change in velocity is negligible here). Then we should be multiplying our final damage by roughly 70x, or 1400d6, averaging 4900 damage!!! Again, this is super pedantic and certainly not valid by RAW, but you get the picture. Key point: the change in velocity isn't that big a deal compared to the huge multiple of mass you're taking on transforming into an elephant.
Again you'll want to remember that you'd be certainly atomizing killing yourself with this maneuver, because the minimum damage you'd do is 1400 (on the infinitesimally small chance you roll 1s on all 1400 d6s), which enough to kill a tarrasque twice over. That is to say, you'd die from massive damage (see Instant Death in the DMG) even if you were a tarrasque PC.
Wasn't sure where to post this, so I went for General Discussion.
So I've been playing around building new PCs with backstory and fun quirks to put in my library. Recently I got onto a speed kick with monk builds but when looking around the boards, most discussions are about utilizing EVERY possible action, extra action, bonus action, etc. for going faster. I, personally, struggle to think of the practical application for that in battle, and it's very niche outside of battle as well. So a practical application of ludicrous speed would be to utilize said speed kinetically.
So, I guess my question is what do y'all think would be the best way to calculate mass bludgeoning damage?
If I multiclass druid of the moon and fly very high in the sky as a giant eagle and then hit "diving speed" as I plunged towards the BBEG, my rough estimate with feats, haste, and boots of speed would be close to 180 mph, WITHOUT using my bonus action. If i then, right before colliding with the BBEG, bonus action transformed into a Huge sized creature like an elephant or a whale... how would you calculate that damage as a DM??
I would start with falling damage, for starters. For each 10 feet you fall, you take 1d6 damage to a maximum of 20d6 at 200 ft. Newton's third law tells us that if you take that damage, whatever you impact should take equal damage. As a DM I'd probably stop right there, and maybe impose disadvantage on a Dexterity saving throw to avoid being crushed due tot he speed and size increase. But we can go further for fun.
For turning into a larger creature, there's no RAW that makes this official, but looking through some other options can help. Animate Objects gives us a clue about how much damage can be done by objects. A huge animated object deals 2d12 + 4 damage on a hit. One could treat dropping such an object as an attack. I would sooner double the damage and call for a saving throw for half, ie. being crushed by a Huge object deals 4d12 + 8 damage or half on a successful Dexterity saving throw. A collapsing roof trap (from the DMG) deals 4d10 damage or half on a successful Dexterity saving throw, which gives us another clue.
Now as for velocity, that's tricky. An object falling without any added force is assumed to fall at a rate of 500 ft/round (from XGtE). Supposing the Monk adds 180 ft. to that movement speed, it would add just over 1/3 to the velocity of the object. If you want to be super precise, you could take the 1d6 damage per 10 ft. above and change the damage scale to reflect this increase. For instance, 20d6 gives an average damage of 70, but you could increase the die to a d8 per 10 ft. giving us a total of 20d8 damage, which gives an average of 90 damage. That's an increase of under 30%, but it's close enough IMO. A d10 would drive up the average damage by over 50%, which is probably too much.
In principle, the average impact force is given by the equation F = (mv^2)/2d, m being mass, v being velocity, and d being impact distance (eg. about 2 meters of impact to flatten a relatively tall human). This implies that mass and the square of velocity should figure together multiplicatively. That dramatically alters the math, but this is already wayyy more pedantic than you want to be at your table.
Edit: Might as well go the full way. Suppose the falling damage we get from the DMG is given as a proportion of impact force.
20d6 ~ (mv^2)/2d
and we assume that an average Medium creature weighs 65 kg, and has a height of 2m. Then suppose you increase the velocity of the fall by 1/3, and increase the mass by a factor of ~70 (assuming you become an average African elephant at ~4500 kg). Then the damage you inflict on a 2 meter creature on the ground should increase by %dM + 2*%dv ~ 70.00 + 2*.33 ~ 70.66 or 7066% (the change in velocity is negligible here). Then we should be multiplying our final damage by roughly 70x, or 1400d6, averaging 4900 damage!!! Again, this is super pedantic and certainly not valid by RAW, but you get the picture. Key point: the change in velocity isn't that big a deal compared to the huge multiple of mass you're taking on transforming into an elephant.
Again you'll want to remember that you'd be certainly
atomizingkilling yourself with this maneuver, because the minimum damage you'd do is 1400 (on the infinitesimally small chance you roll 1s on all 1400 d6s), which enough to kill a tarrasque twice over. That is to say, you'd die from massive damage (see Instant Death in the DMG) even if you were a tarrasque PC.