How do I handle my players killing things by catapulting a folding boat?

Question

So, I'm not sure where to begin...

I planned some epic battle and "that guy" showed up and ruined it. He took a magical item I (stupidly) gave him (folding boat, DMG 170), cast Catapult (EE, p.15) on the item and said the magic words while it was in air. The small package opened up to a large boat. He threw a large boat at the bad guy. We all laughed... it was very creative.

I ruled it did the 3d8 damage from catapult, plus 5d8 "boat" (bludgeoning) damage. I like to reward creativity.

My issue is... he still has the boat and plans on doing this repetitively. How can I take this item back / break it without being the mean DM? Can I do damage to the magical item?

The instant fortress item can be damaged, and only repaired by Wish (which seems excessive for a boat).

I will also add, I didn't accidentally give them this item, I'm running a high magic campaign. The boat, while wondrous, I think isn't a legendary item. Maybe I can't have it both ways ("here have these magical items, but don't use them weirdly").

Answer 1

The folding boat explicitly says that it takes an action to speak the command word. If your player is using his action to cast catapult, he doesn't have an action left to properly incant the command word before the attack finishes.

The catapult spell says that it targets an item weighing "1 to 5" pounds, and it propels the target "in a straight line". This isn't throwing the item, it's moving it magically. If the item ceases to be a valid target for the spell (because it weighs too much), the spell fails and the item falls to the ground.

The catapult spell deals equal damage to the thing being thrown as to the target. The foldable boat probably can't take too much damage before it stops folding properly.

Finally, it's not clear from the folding boat description how long it takes to gain all that mass. If you don't think explosive decompression is reasonable, you might rule that the unfolding process takes a minute or two.

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The players have already used this once and seen that it worked. I recommend being honest with them: "Guys, the boat-catapult thing worked once because it caught me by surprise, but I went and looked at the rules more closely and I have the following concerns. We'll leave the result of the previous combat as it happened, but if you try it again, we'll follow the rules correctly."

Answer 2

Oh, there's a few ways you can tackle this.

1. Be a rules lawyer Catapult says it does 3d8 damage. So it does 3d8 damage. RAW. It's crude but efficient. The downside is that it's not very much fun.

2. Be realistic - even if they don't want you to be. This is my preferred option, because it (a) does reward them for being creative, and then (b) punishes them for overusing it.

So, they've thrown a box at their opponents, and then mid-flight they're transforming it into a boat. To my mind, two things are about to happen:

First, you now have a boat in midair, complete with a mast and sail. As seen on Mythbusters, hydrodynamic and aerodynamic are not interchangable traits. Add the fact that a big ol' sail has gotta mess up the trajectory, and I'd feel totally justified in breaking out the scatter rules - that boat is probably not going to land where they were aiming.

Second, they just dropped their boat from a significant height, and boats are not designed to take those sorts of forces. As a quick-and-dirty rule, simply say that the boat takes equal damage (Newton's 2nd, after all).

Answer 3

My answer is a variation on the theme of "the boat takes equal damage". Your problem now is how to introduce this gracefully.

This should come into play the next time he uses the boat, either as a boat or as a boatapult.

• If he uses it as a boat, make the existing damage obvious, such as pointing out it's sprung several leaks, and needs constant bailing out to keep it from sinking.
• If he pulls the boatapult again, point out that the boat is now looking much worse for wear, and that it would probably only survive one more catapult. You can also point out that boats weren't designed as siege ammunition.

At that point if he spends gold to fix it before catapulting again, you've balanced it. You should definitely figure out how much you think he should spend to fix the boat before he asks.

Answer 4

I'd say it's up to you as the DM. A couple questions I would ask myself in this situation:

1. What kind of campaign are you running? Is this more for social fun and creativity, or a strictly rules-based campaign? If you're going for fun and casual play, I'd follow the scatter rules AllenGould mentioned in his answer. Leave it fun and creative but give them incentive to find another solution. If you're going for more rules-based, then I would just say make an enemy who can destroy the boat and then call it good.

2. Is this something you really want to nerf? Do you enjoy the creativity and fun in this and want it to keep going, or would you rather they find another solution? Ultimately, as the DM, it's your call in this scenario, so go with your gut on this.

3. Can you use this to up the difficulty of the campaign? Is this something you could use to change up the mechanics and reward them while punishing them at the same time? Personally, this would be my solution. Reward them by letting them keep it, but power up your monsters and enemies so they can no longer be unnecessarily challenged by a catapult boat.

In the end, obviously all we can give you are suggestions. You're the DM and it's going to be up to you to decide what to do. Hope this helps!

Answer 5

Throwing your weapon at the enemy is just disarming yourself with style. Magic items are rare, and whoever they're fighting might be all too happy to cut their losses, collapse the magic boat, and hoof it.

Answer 6

The real problem here isn't that you've got an overpowered weapon - The Catapult does what the catapult does - the problem is you made an exception (it does 5d8 extra damage), and now the players want to keep using it that way, but you don't want them to cheese every fight by firing boats.

The practical, reasonable solution to this is to own up to the fact - that you really only wanted to reward a one-off for clever thinking, and that you really do not want them to keep using it like this, and that '5d8 boat damage' is house rule, one that you aren't going to continue to uphold.

They may complain about it, but you have to hold firm to this - I cannot remember the question from this site that said it, but one very smart answer once said "If the rules speak differently than what the DM ruled yesterday, then those were the rules for yesterday, and only that day".

In short - you made an honest mistake in allowing the players to have an overpowered weapon. Don't erase that, just let them know you aren't going to let it happen again. If they really are as clever as all that, they're sure to come up with something new that's better than a boat.

Answer 7

Besides all the great alternatives already presented:

You might want to let the PCs keep and use the trick -- at least as long as the Enemy (who or whatever that may be) figures out the three command words needed for the operation of the boat. You know, survivors might overhear those command words. Or spells may help a resourceful opponent learn it. And so on. Once the enemy knows the words, have them use those words in combat. Unfold the boat in the PC's backpack or hands unexpectedly, turning their own weapon against them. Or have them turn it back with a readied action, and nick it (as SPavel recommended it in his answer (which I upvoted, of course)).

Or simply have the Enemy (or one of its minions) ready and use a Silence spell with which command words (also) can be made impossible to use for a while.

Answer 8

You said it's a high-magic campaign, so it's reasonable to assume that the PC's enemies have magic items at their disposal as well. Scrying magic is fairly low-level; so there was an NPC that scried on the party when they pulled this trick the first time, learning the command words the party used.

The next time the PCs throw their boat at someone, that someone is now the NPC in question, and he's prepared. He does any of the following (DM's choice):

• Grows the boat in the PC's hand just before he throws it
• Shrinks the boat in midair and catches it in a Bag of Holding (boat can't "hear" the command word to expand while it's in there)
• Casts Baleful Transposition to switch places with either the squishiest PC, the biggest threat, or the healer, while the boat is in flight

Answer 9

Ignoring that you have set incorrect expectations for your players, you should treat this boat catapult, at best, like you would any other 'improvised weapon'. Perhaps a total damage of 2d8 if it hits a stationary, large target.

The way physics works is that objects' momentum is conserved, not their velocity. You can see this by spinning around in an office chair, and then sticking your arms out to the side. Your (angular) velocity decrease, but your (angular) momentum is conserved.

Lacking anything magic that breaks physics, physics still applies. The item's description doesn't say anything about what happens to the item's velocity or momentum, so we use physics.

So, what would happen is you fire the boat, it travels at roughly the same velocity, mass and momentum as a rock. It would do less damage than a rock because it is not as hard, spreading the impact over a larger area. Momentum does more damage if it is concentrated on a small area, this is why knifing someone does more than punching them.

Then, you turn it into a big boat. It's mass increases instantaneously, and it's velocity decreases instantaneously. The momentum is the same as the folded boat, which is the same as the rock.

If the player timed this perfectly (so that the boat hits the target immediately after expanding), then the ship packs as much of a punch as the folded item or the rock. However, this is spread over a much larger area than either rock or folded item and does less damage accordingly.

If the players were to speak the command word half way through the trajectory, the ships velocity would be nearly zero, and it's cross sectional area would be massive. It would essentially drop from the sky where it was when you spoke the words.

It is perfectly acceptable in DnD to make up rulings on the fly to keep the game going, and then decide something later that contradicts this after thinking for longer.

Answer 10

A big boat will probably collapse under its own weight alone, if not supported by the water or an elaborate drydock rig. A smaller boat may survive its own internal forces, but no boat is designed to survive being catapulted.

I'd say the first use is ingenious, and reward it as much as it makes sense, but at the expense of the boat. The villain is probably dead or badly whacked up, but you have a folding wreck now instead. Maybe it cannot fold anymore, or if it does, it unfolds into the same wreckage. It is no longer usable as a seaworthy boat unless repaired at the magical shipyards of Unreachia. (hope they have deep enough pockets).

If they try to catapult it a second time, it may work. Sort of. As an area-effect weapon, spraying an area with timber, planks, rope, cloth, tar, or even a few cannon if the boat is armed. That could also hurt the targets a lot (maybe the standard 3d8 catapult damage for everyone in the target area, friend and foe) but then the boat is now "scattered" as well as "destroyed".

Answer 11

You could do this in such a way that makes the bad guy seem badass, breaks the item and leaves the party desperately panicking, with a little tinkering. In pathfinder there's a maneuver called "sunder", where a character (or bad guy / monster) can make an attack against an item being held or worn by a creature and attempt to destroy or break it.

You could have the big bad ready an action while the players plan their little boat-a-pult maneuver. When they fire, roll a d20, either fudging it or if you somehow manage a good enough roll. Big bad guy cuts the boat down it's length by holding out his killdeathanator sword, splitting it down the middle before shooting them a smug smirk. Problem solved, player privilege checked, bad guy set up as a badass, balance restored.

And best of all, it all adds to your game and makes you look like tony stark at the jericho missle reveal test.

Of course this may be a tad too late. But if they ever do it again, remember me.

Answer 12

Next time he launches a boat at somebody, the target tries to shoot it down, and damages it a bit.

Next time after that, the target tries to shoot it down, and punches a good-sized hole in it.

Just make it clear that this tactic may continue to pay off, but that they run the risk of losing the boat.

Answer 13

There's always the option of designing encounters where the boat won't work, like an encounter in a confined area, or where it's extremely hot and the boat would catch fire.

For extra fun, do an encounter after a couple where using the boat wouldn't work and, if it isn't destroyed by then by attempts to use it anyway, the new foe heard about the boat thing and came prepared...

Answer 14

Loving the answers to this one almost as much as the idea of throwing a magic boat at people. Gotta love inventive players, even when they mess up your carefully laid campaign.

Scott's treatment of the physics of the problem is great, but might be missing the application of magic to the issue.

The description of Catapult I found reads (in part):

Casting Time: 1 action

Range: 150 feet

Components: S

Duration: Instantaneous

Choose one object weighing 1 to 5 pounds within range that isn't being worn or carried. The object flies in a straight line up to 90 feet in a direction you choose before falling to the ground, stopping early if it impacts against a solid surface.

This indicates that the spell is moving the object but not imparting momentum to it. Which makes sense since, as an instantaneous spell the momentum would be infinite anyway. In a science framework this would be immediately objectionable, but we're using magic so I have no issue with it. It's just a teleport spell with some odd side effects.

The remainder of the description talks about the damage done - (cast level + 2)d8 - and the maximum mass if the object - cast level * 5 pounds. The actual mass of the moved object doesn't factor into the calculations of the damage or how far the spell can move the item, these are set as parameters of the spell itself. This is why there's no difference between using Catapult on a 1lb bag of feathers or a big old ball of sharpened spikes.

So what happens if you cast Catapult on a Folding Boat and invoke it in transit?

According to the spell description above you actually can't do this. The duration of the spell is instantaneous and as such you can't perform any other action during it. The Folding Boat would disappear from one place and immediately appear in another, unfolding either before or after the move.

So even if you time your activation as close as possible to the release of the spell, the unfolding will either happen before or after the spell effect takes place. If before then your folded boat is transported and strikes the enemy, both taking 3d8 damage from the spell, then unfolds. If before then the boat takes on mass that makes it an invalid target for the spell and thus the spell fails, causing no damage to either boat or target.

Let's assume that the unfolding of the boat takes time and is starting to happen when the Catapult spell affects it. Nothing changes except for the location of the boat as it unfolds.

So... +5 points to the players for style and imagination, -10 points for feasibility.

I can still think of a few ways that could be useful, such as knocking somebody down with the folded boat and then trapping them under it as it unfolds, or firing the boat into an enclosed space and having it crush the contents against the walls as it unfolds, but I'm pretty sure any GM I know would rule at least one of those out of practical use.

Answer 15

Conservation of Momentum

• Initial weight of box: 5 lbs or ~2.5kg

• Assuming speed of a fast arrow for the catapult spell: 200mph or ~90m/s

• Momentum of flying box: 225kg⋅m/s

• Weight of ship (assumed): 20000kg ~viking longship

• Velocity of ship: Momentum/Mass = 0.01125m/s

• Speed of a brisk walk: 1.1m/s

“How do I stop my players from killing things by catapulting a folded boat?” The boat moves really, really slowly once unfolded – about 100× slower than a brisk walk. The intended target starts to really wonder why you conjured a boat in the middle of the fight.

But what about, you know... Magic

Physics still works in the absence of magic. The spell's already been cast, and has a limited power level. If you wanted to fire a boat at the same speed as an arrow, you'd require a significantly higher level spell that would cost much more than catapult.

Just like fire from a spell behaves like mundane fire once the spell is over – which is why casting burning hands in a barn is a bad idea – So does the boat.

Which is why casting catapult at level 9 only gives you the ability to move an object of 45lbs. The energy of the spell just isn't that much, and definitely not enough to move an entire boat this way. The magic still works (boat is still moving forwards), but the spell was never made to cope with something this big correctly.