The Kick is GOOD! (Casual knockback in DnD games)

Setup

I got a Steam chat from someone with whom I regular interact over that channel. He was wondering out loud if Dungeon Grappling includes rules for kicking.

My first response was “that’s just an unarmed strike; DnD doesn’t do that level of specificity.” Fine, if unsatisfying.

Then he noted that what he really wanted to get a feel for, having been playing through Storm King’s Thunder, is why not have rules for a Storm Giant knocking a halfling across the battlefield like a ping-pong ball?

Ah! Well, yes. Dungeon Grappling does have rules for Flinging and Shoving, where you grapple someone and then you can use the rules to shove or fling them a certain distance.

Incidental Projectile

That got me thinking, though. There are of course rules for this in DnD, but not for incidental contact. You have to deliberately decide to shove your foe, which Dungeon Grappling extends to flinging.

But hrm and hrrrm, this is where game design rears its head. For whatever reason, the designers decided to make shoving a different mechanic than striking. One is a contest of Strength, the other a damage roll. There are reasons for this, of course, and those reasons are at the very least defensible.

But there’s a cost to this. An Ancient Red Dragon’s tail swipe does 2d8+10 damage from a Gargantuan creature. So 12-26 points. for a creature that might be the size and mass of a house. I’ve seen some pretty large imaginings of these guys, but even without, the basic size for a Gargantuan creature is 20′ x 20′ (or larger). So the size of a small two-car garage or so.

It would be interesting to relate size and damage to knockback power, though, so it’d be possible to have the Cave Troll knocking hobbits about.

This would mean finding a scale of damage that maps well to knockback, and a sensible mapping of such.

Rules for Rules

It should be simple, though, and for equal foes, not change the game much. So what do we want to do?

  1. The basic flow of play should not change. An attack should be done with the usual stuff, culminating in a damage roll.
  2. It would be best to not involve extra rolls, so this means determining some sort of target number. That number needs to be high enough that most damage rolls by (say) medium-sized creatures will not cause folks to be knocked around or down.
  3. We will need to consider if the damage scale in 5e is sufficient to cause the kind of effects we want, or if we’re to invoke size class. The first is better, the second may be necessary.

OK, so let’s do this.

A typical not-fighter character will do damage in the 1d6+2 range per attack (non-martial weapon, STR 14) for a damage range of 3-9. A fighter or barbarian type is often looking at 1d8 to 2d6 +3 to as high as +7, but mostly +3 to +5; a range of 4 to as high as 17 or so. An Ancient Red Dragon, one of the nastier and larger critters out there with STR 30 does 2d8+10 damage with a tail swipe, and 2d6+10 with a claw. That gives a range of 12 to as high as 26.

Incidentally, this right here tells me that I will almost certainly need to invoke size modifier here. A gargantuan dragon should have way more “knock you around” potential than maybe 1.5x as much as a powerful barbarian, because size. In fact, I have to wonder if the gargantuan dragon’s base damage should follow a higher progression, perhaps being closer to 4d12+10 for the bite, 4d10+10 for the tail, and 4d6+10 for each claw. Then with a maximum oomph of 50 points, relative to a fighter’s 17, that’s at least 3x, which while maybe not enough it’s at least something.

What to compare it to? Strength, clearly. Adjusted for the creature’s Size Class. So a Medium average guy would have a threshold of 10. No regular hit with a non-martial weapon will knock this person down, though a crit might. That passes the smell test. A Small creature with STR 10 would have a threshold of 7 or 8. So maybe, but unlikely for non-martial types, fighters will knock a foe down or move them around with reasonable frequency, and for both medium and small creatures, a dragon claw or tail will move you every time, even without SM.

Cut to the Chase

In short, roll damage, multiply by size modifier from Dungeon Grappling, compare to STR. If damage is less than STR, no effect. If damage is equal to or greater than STR, then you get knocked Prone (make a STR save vs the adjusted damage) to keep your feet, and for every multiple of your STR you get moved 5′. Or you can have it so that the first multiple is just getting knocked prone, and displacement is each multiple after that. If you’re moved 5′ or more, you automatically are knocked prone.

Edit: It occurs to me that better than STR might actually be a flat target number. This is easier to remember, and ensures that play is fast. If so, I’d say Tiny is 5, Small is 8, Medium is 10, Large is 15, Huge is 20, and Gargantuan is 40. If you want to go nuts, add the STR modifier to that total, but then you’re back to calculating a new value for every type of creature.

The post continues with the original STR idea, but a flat target number, or a flat number modified by a bonus, will give more uniformly applicable results.

Oh, and you suffer damage as per a fall from half the displacement when you land. Full displacement if you get knocked into a wall.

So:

Non-martial character, damage likely ranges from 1-9 points, 2-14 on a crit. On a Medium target of STR 10, they will never knock them 5′ back, and mostly nothing will happen. Worst case is a save to be knocked down. Against a ST 8 small creature (adjusted scale 6), you might knock ’em down, or even knock ’em back 5′, but only on a very solid crit that does 12 points of damage.

Martial character likely ranges from 3-17 points, with crits being as high as 9-29. Against a medium target of STR 10, mostly you might knock someone down, and on a crit might knock them 5′ back (10′ if you can eke out 30 points). If they’re stronger, like STR 18 or so, you won’t even do that, and mostly will not even knock them down on a regular strike, but might on a crit.

An ogre vs a medium character is 2d8+4, multiplied by 1.5 for being large, so 9-30 points, with 12-54 on a crit (4d8+4 x 1.5). Now we’re talking – a max damage blow can send a humanoid of average STR up to 4 spaces, or 20′. Against a small character with a threshold of 8, up to 25′.

Dragon? Well, as listed, they “only” do 2d8+10, but the x4 size mod means that on a hit the knockback potential is high. 12-26 regular damage, 14-42 on a crit, x4 for size. So even a mild swipe will look at 48-104 points of knockback, and a crit is as much as 168, which can send a human of STR 10 something like 75′.

 

Parting Shot

Fights in DnD are not counted in the currency of realism. They are epic and counted in the currency of awesome. Fighting big creatures when you’re little is never a good thing, and such fights should be awesome to contemplate. Getting knocked around like this also makes formation fighting harder, as the bad guy can pull a Sauron on you and just scatter troops about with casual blows – something that is not “incidentally” possible with the current rules.

This was just a starting point, but the results don’t feel horrible, though some Monte Carlo work would be useful to see if there are degenerate cases or exploits.

It would also be reasonable to restrict this to bludgeoning damage, thunder damage, and other things with physical force behind them. Piercing isn’t going to knock you around that much, fire burns rather than shoves, etc.

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