Gargantuan isn't really that big

[Greywander]

Big for a person? Sure. Big for a house? That's going to be a cramped apartment.

I'm working on a homebrew class that allows the player to turn into a vehicle, starting as a fun-sized personal mecha and scaling up to a gargantuan titan. And yes, I'm starting to see why this doesn't work very well as a player option, so I'm not here to talk about that. Everything I say here can be applied to more traditional vehicles as well. I'll also head off one particular discussion by saying that, no, Enlarge/Reduce doesn't work, because allowing you to be affected by transformation effects while you're carrying passengers is asking for a tragic accident to happen. I'll also say that you can revert to a smaller vehicle size, e.g. to follow the party into a dungeon.

As I said, you scale up from medium to gargantuan, but gargantuan isn't really that big. You occupy only a 20x20 foot space, while a typical warship is going to be closer to 100 feet long or longer. Now, gargantuan is actually 20x20 "or larger", with no upper limit, something I'm banking on by allowing you to carry more than 100 passengers. Pretty crazy, but most things in tier 4 are. So the "or larger" clause means we can technically let the player be as big as they want, though for mechanical reasons they'll still probably only occupy a 20x20 space.

What about the smaller sizes? Well, things seem to have worked out to give a pretty smooth progression in terms of your function as a party vehicle. In tier 1, you can only carry one person, so you're more of a personal mount than a party transport. In tier 2, you can become large and carry up to 5 passengers, which is far too small to be used as a mobile home base, but perfect for a party transport. Why book passage on a ship when one of you can be the ship? Except 5 passengers might be a bit generous for a large sized vehicle. Remember, a horse is also large. Though a carriage could probably fit in a large space, too, and could easily carry 5 people. It helps if we assume some passengers are just along for the ride and don't have room to fight. A large space is 2x2 squares, which is enough for four medium creatures, but we can also assume some verticality, so with a 2x2x2 volume, you can fit up to 8 medium creatures. Except that's not all empty space; you/the vehicle is there, too. So 5 passengers is at least plausible, but it will be a bit cramped.

In tier 3, you can grow to huge and carry up to 20 passengers. Now you can actually serve as a home base, albeit a small one. Really small, in fact. A huge creature is 15x15 feet, which comes out to 225 square feet. If we assume you have three decks, that's a max of 675 square feet, and that's assuming you physically take up the entire 15x15 space (and most creatures don't, e.g. humans aren't 5 feet wide) and that you don't need any of that room for internal components, which you will. If we imagine a modest sized ship that can serve as a small home base, we're probably looking at something 40 feet long at least. Which, again, brings us back to something larger than gargantuan.

I think for mechanical reasons I'll have to stick with the sizes I've got, but it's pretty clear that the size system was never intended to be applied to things like buildings or large vehicles. Which I guess is just another point against making this a player option. Still, I intend to press on and see if I can't make something that at least kind of works, and could be quite fun to play.

[PhoenixPhyre]

Gargantuan, like tiny, isn't a fixed size. It's a minimum for gargantuan and a maximum for tiny. Nor is it the actual size of the object, but the space it controls in combat. Those are very different things. And not conflating them makes this go away.

[Unoriginal]

I feel like if you want a PC to become a Gargantuan+ vehicle, using the vehicle combat rules and giving the vehicle-PC special actions would be the easier way to go.

[Greywander]

Gargantuan, like tiny, isn't a fixed size. It's a minimum for gargantuan and a maximum for tiny. Nor is it the actual size of the object, but the space it controls in combat. Those are very different things. And not conflating them makes this go away.
But usually the space a creature controls is larger than the creature's physical size. It wouldn't make much sense to have a 100 foot warship that only controls a 20x20 space. And while gargantuan can scale up, the same isn't true of smaller sizes, such as large and huge.


I feel like if you want a PC to become a Gargantuan+ vehicle, using the vehicle combat rules and giving the vehicle-PC special actions would be the easier way to go.
The what.

There are vehicle combat rules? I'm AFB right now, but some quick googling isn't turning up other than homebrew.

[PhoenixPhyre]

I feel like if you want a PC to become a Gargantuan+ vehicle, using the vehicle combat rules and giving the vehicle-PC special actions would be the easier way to go.

I'd agree.

But the issue even exists for transforming into Gargantuan creatures (such as shapechange into a Purple Worm). Or even nominally Huge ones (adult dragons, for instance). There is just absolutely no way an adult dragon fits into a 15x15x15 cube. Not unless they're compressed. Or our favorite discussion about forcecage/wall of force in the dome configuration. Which is why it's important to note that
a) physical size and combat space are only weakly correlated, especially as you move away from Medium in either direction. And even Medium, especially in the vertical direction (most humanoids are well over 5' tall, some are closer to 10' than 5').
b) Gargantuan is 20x20 or bigger; tiny is 2.5x2.5 or smaller[1].

So a "turn into a vehicle" thing would just specify the size and space taken up. Heck, even the Saltmarsh ship rules do that--they have Gargantuan (LxW) in their statblocks.

[1] No, your average spider is not 2.5' in either dimension. Or even controls that much area. Unless you live in Australia, in which case, carry on. And carry a flamethrower.


But usually the space a creature controls is larger than the creature's physical size. It wouldn't make much sense to have a 100 foot warship that only controls a 20x20 space. And while gargantuan can scale up, the same isn't true of smaller sizes, such as large and huge.


Not really. The easiest examples are things with wings--a young dragon is only Large...but they have ~20' wingspans and tails that go way above 10'. Also things with a vertical dimension--goliaths start (before MoTMV) at ~6'5 and go up from there. The shortest giant is 15-ish ft tall, but is Huge. Most are 20+. Something like a dragon can't fully control all the space it occupies--people can easily dart under the wings or even under the body for a big-enough one.

Basically, think of space controlled as varying slower (in either direction) than physical size, with Medium being the closest fit. But still not a good one--the "proper" closest fit is the Gelatinous cube (which has a trait saying it occupies its entire cubic volume controlled). Everything else is off in one direction or the other. But not consistently so.

Personally, D&D's combat space abstraction breaks down badly when you have PCs that spend significant time outside the Small -- Large band. And Large is already pushing it, and Small mainly works because it's identical to Medium. Having someone regularly turning into something even Huge is going to expose a whole bunch of weird edge states that have never been tested or smoothed out. And you're going to have to do a bucket-load of work to smooth them out. Or may not even be able to.

[Asisreo1]

But usually the space a creature controls is larger than the creature's physical size.
Not at all. The average height of most medium humanoids are above 5'. Tall humanoids even get to the 6' and above range for average height.

A Roc's wingspan spreads over 200ft, canonically, and they're also considered "Gargantuan."

In the DMG, page 248, the Giant is represented as "Huge" despite her height being far closer to 20ft and in fact, a little above.

[Segev]

Yeah, I think D&D 5e's "simplification" of the size categories by reducing the number of them was a mistake, honestly. Even 3.5 ran into trouble at the edges, but at least it took a lot longer to get to "Colossal+" when you had a decently-large range for "colossal" that still kept it kind-of reasonable on its grid template.

Fortunately, outside of grapple rules, size categories don't matter a whole lot. You can just increase the grid template as you get bigger even if you still count as "Gargantuan." Or, you can introduce "Colossal" as a size category if you want to.

[KorvinStarmast]

Yeah, I think D&D 5e's "simplification" of the size categories by reducing the number of them was a mistake, honestly...Or, you can introduce "Colossal" as a size category if you want to. I think that would have been useful for this edition.

[Greywander]

There is just absolutely no way an adult dragon fits into a 15x15x15 cube. Not unless they're compressed.
Hmm, that's a good point. This can even apply to a lot of mundane snakes, too. However, those creatures can at least coil up to fit within that space. You can't really fold up a tank or battleship.


Which is why it's important to note that
a) physical size and combat space are only weakly correlated, especially as you move away from Medium in either direction. And even Medium, especially in the vertical direction (most humanoids are well over 5' tall, some are closer to 10' than 5').
b) Gargantuan is 20x20 or bigger; tiny is 2.5x2.5 or smaller[1].
That makes sense. Your size category basically acts as your strictly mechanical size, but your in-universe size might be bigger or smaller than that. It's basically a game abstraction to make the game a little easier to run.

As for tall humanoids, I've mentioned before that the math used for the properties of different sizes suggests that there's a missing size between medium and large that should take up roughly a 7x7 foot space. Likewise, small creatures should actually take up a 3.5x3.5 foot space, but since that's too big to fit more than one such creature in a 5x5 space, it just rounds up. Anyway, I think the missing 7x7 size would have been a good fit for creatures like centaurs and goliaths.


[1] No, your average spider is not 2.5' in either dimension. Or even controls that much area. Unless you live in Australia, in which case, carry on. And carry a flamethrower.
If you're getting into actual combat with a spider, a cat-sized fantasy tarantula doesn't sound unreasonable.


Not really. The easiest examples are things with wings
One houserule I've heard to help weaken flying races is to require enough space to spread their wings. This could be run as a medium creature actually occupying a large space while flying, though there are a few different ways to handle it. My point is that the general assumption seems to be that wings don't figure in to a creature's size, though that does seem rather arbitrary.


Something like a dragon can't fully control all the space it occupies--people can easily dart under the wings or even under the body for a big-enough one.
But isn't this already accounted for by allowing smaller creatures to move through their space? Or does this have more to do with things like OAs?


Having someone regularly turning into something even Huge is going to expose a whole bunch of weird edge states that have never been tested or smoothed out. And you're going to have to do a bucket-load of work to smooth them out. Or may not even be able to.
That's not the only tricky thing I'll need to sort out, but it certainly is a big one, pun intended. Abstraction is probably the way to go here: you determine your appearance while transformed, which can include size and shape, but mechanically you are large/huge/gargantuan. Abstraction can create a disconnect between what's happening mechanically and the reality it is supposed to be simulating, but that will probably lead to fewer headaches than trying to make the rules line up exactly with the roleplay.

[Unoriginal]

The what.

There are vehicle combat rules? I'm AFB right now, but some quick googling isn't turning up other than homebrew.

Ship combat rules are in Ghosts of Saltmarsh, land vehicle combat rules are in Baldur's Gate: Descend into Avernus (and I think the supplement "Infernal War Machines Revisited".

[PhoenixPhyre]

Hmm, that's a good point. This can even apply to a lot of mundane snakes, too. However, those creatures can at least coil up to fit within that space. You can't really fold up a tank or battleship.


True. But D&D is centered around creatures, not tanks or battleships.



That makes sense. Your size category basically acts as your strictly mechanical size, but your in-universe size might be bigger or smaller than that. It's basically a game abstraction to make the game a little easier to run.

As for tall humanoids, I've mentioned before that the math used for the properties of different sizes suggests that there's a missing size between medium and large that should take up roughly a 7x7 foot space. Likewise, small creatures should actually take up a 3.5x3.5 foot space, but since that's too big to fit more than one such creature in a 5x5 space, it just rounds up. Anyway, I think the missing 7x7 size would have been a good fit for creatures like centaurs and goliaths.


That goes for 99.99999% of "this makes no sense" cases. It's a game abstraction and better not to worry too much about.



If you're getting into actual combat with a spider, a cat-sized fantasy tarantula doesn't sound unreasonable.


Not just spiders. Familiars and fitting under doors, etc.



One houserule I've heard to help weaken flying races is to require enough space to spread their wings. This could be run as a medium creature actually occupying a large space while flying, though there are a few different ways to handle it. My point is that the general assumption seems to be that wings don't figure in to a creature's size, though that does seem rather arbitrary.


Force cage. Just..force cage.



But isn't this already accounted for by allowing smaller creatures to move through their space? Or does this have more to do with things like OAs?


Auras and other "from you" effects. AoEs. OAs. Reach. And even with the "smaller creatures can move through", they treat it as difficult terrain.



That's not the only tricky thing I'll need to sort out, but it certainly is a big one, pun intended. Abstraction is probably the way to go here: you determine your appearance while transformed, which can include size and shape, but mechanically you are large/huge/gargantuan. Abstraction can create a disconnect between what's happening mechanically and the reality it is supposed to be simulating, but that will probably lead to fewer headaches than trying to make the rules line up exactly with the roleplay.

Yeah.

[Hytheter]

I think some of you are forgetting that the creature size-defined space a creature occupies is a square, not a cube. The reason 8' humanoids can be medium is because medium is defined as occupying a 5x5 space, not 5x5x5. Likewise for 20' giants in 15x15 spaces. Vertical space is not mentioned in the passage about creature size at all. (Verticality is a poorly-supported aspect of the game in general, actually, despite coming up all the time in play.)

Of course, creatures with long necks and wide wing-spans fitting into spaces they rightly shouldn't are another matter.

As an aside, I find it bothersome that gargantuan is stated to be 20x20 or larger yet no monster has a specific size listed in its stat block. Are we just supposed to guess?

[Asisreo1]

As an aside, I find it bothersome that gargantuan is stated to be 20x20 or larger yet no monster has a specific size listed in its stat block. Are we just supposed to guess?
Most of the time, yeah. But I do know that the Tarrasque is said to be 50ft tall and 70ft long.

[Segev]

If you're getting into actual combat with a spider, a cat-sized fantasy tarantula doesn't sound unreasonable.

There is something amusing about the pact of the chain warlock who has a tiny black widow spider as his familiar sending it into combat with the expectation that it "commands" a two and a half foot square space.

[JLandan]

I've always used a system of approximating height, as opposed to space, that doubles each previous category.

S apx. 3'
M apx. 6'
L apx. 12'
H apx. 24'
G apx. 48'

C (if used) apx. 96'

I've found it works okay for approximating length as well.

[Greywander]

Or, you can introduce "Colossal" as a size category if you want to.
I've done some work expanding the number of sizes, both up and down, and also bringing in the missing 7x7 size. The thing is, any such modification would require going through all the monsters and sorting them into the new size system. So it's not really useful as an addon for 5e and would work better for an original system, or at least an original setting with it's own list of monsters.

But as you expand the size system, it becomes more cumbersome to use. Ideally we want to expand it infinitely in both directions, but that's not really practical. However, while thinking about it just now I may have come up with a slightly better system that can handle an infinite number of sizes in a more elegant way.

First, every creature would be assigned a number that gives their absolute size, probably with humans at size 0 and anything smaller uses negative values. This allows us to easily extend the size system infinitely in both directions. Then the rules for interactions between creatures of different sizes would be written in relative terms. For example, a "small" creature always refers to a creature one step smaller than you, regardless of your actual size. After a certain point, a creature much bigger or smaller than you isn't going to interact with you any differently, so we can get away with only making a few relative size categories where the rules are actually different. This leads us back to a place where "tiny" can mean "this size or smaller" and "gargantuan" "this size or bigger", except now it's in relative terms instead of absolute terms. This allows the game to handle everything from Kaiju battles to Fantastic Voyage without artificially scaling everything up or down.

If course, this has the same issues in that you need to sort all the monsters into their new sizes, so it's not really any more feasible to implement. But it could work well for an original system.

[Imbalance]

Miniatures. Just sayin'.

[Joe the Rat]

I run entirely VTT, and the "space controlled" would explain why you wouldn't want to trim an image to the token border for Truly Colossal opponents.

But then, when I am doing Truly Colossal, I plunk down a non-pog token that is as big as it is.

[PhoenixPhyre]

But then, when I am doing Truly Colossal, I plunk down a non-pog token that is as big as it is.

For one gonzo oneshot, I used toy dinosaurs as "minis". Because they were fighting a family of tarrasques who had been upgraded by WH40K orks that had gotten lost in the warp and ended up in a fantasy realm. But being orks, their "tech" still mostly worked. So they befriended and up-armored/up-gunned a trio of tarrasques. The big one was probably 10-ish inches tall and I had attached markers (buttons glued to a ribbon so I didn't have to actually permanently modify the toy) for the various weapon and shield emplacements.

[Envyus]

For some examples of Gargantuan Minis

https://assets-prd.ignimgs.com/2022/02/24/wk-grd-2022-720-1645670684873.jpg
https://i.imgur.com/8V95JFX.png

[SociopathFriend]

For some examples of Gargantuan Minis


The hell is that second one?

[JackPhoenix]

The hell is that second one?

Astral Dreadnought. Also known as "that thing cacodemons in the original Doom copied."

[Imbalance]

https://giftedvision.com/wp-content/uploads/2015/08/101-Kraken-PPM.jpg

https://www.minisgallery.com/forum/phpBB3/download/file.php?id=8538

https://cdn.shopify.com/s/files/1/0266/7400/4031/products/2ljdmvfssgi27gld1myg_dnd-purpleworm6_3e146af7-d568-4337-adce-156854067b8f_1024x1024.jpg?v=1651779651

https://giftedvision.com/wp-content/uploads/2018/03/shop_behemoth_ppm.jpg

https://wizkids.com/wp-content/uploads/2020/08/galactus-630806-cVN6CrBH.jpg

https://i.ebayimg.com/images/g/VigAAOSw5k5gw-zH/s-l500.jpg

https://static.wikia.nocookie.net/swminis/images/e/e3/SW_miniatures_AT-AT_imperial_Walker_Colossal_Pack.jpg/revision/latest?cb=20090707111948

https://cdn.shopify.com/s/files/1/0266/7400/4031/products/war-machine8_0a9cafd1-78e4-4824-9490-f32be5eb0f1a_1024x1024.jpg?v=1651776522

[Eldariel]

You could just go Warhammer, say "screw sizes", introduce miniatures and effect size markers and just use those instead. You don't really need a grid for anything and making the grid go away makes all these problems go away. Though yes, the size rules of this edition are terrible, by and large. They don't even help run the game any more efficiently. 3.0 had it better but meh, baby with the bathwater and all that.

[Segev]

You could just go Warhammer, say "screw sizes", introduce miniatures and effect size markers and just use those instead. You don't really need a grid for anything and making the grid go away makes all these problems go away. Though yes, the size rules of this edition are terrible, by and large. They don't even help run the game any more efficiently. 3.0 had it better but meh, baby with the bathwater and all that.

Doesn't make all the problems go away. Size still matters for things like grappling. A house spider can technically grapple a halfling. A hill giant can technically grapple a sentient planet.

[Eldariel]

Doesn't make all the problems go away. Size still matters for things like grappling. A house spider can technically grapple a halfling. A hill giant can technically grapple a sentient planet.

True. But you can just Rule 0 what can grapple what. The steaming pile that is 5e size rules is worse than nothing.

[pothocboots]

Doesn't make all the problems go away. Size still matters for things like grappling. A house spider can technically grapple a halfling. A hill giant can technically grapple a sentient planet.

Maybe it would be better to just lean into it. If we remove the size restriction on who can be grappled I'd expect to see more of it, especially from smaller characters, and I'm fine with that.

I want spiders grappling giants.

[Segev]

Maybe it would be better to just lean into it. If we remove the size restriction on who can be grappled I'd expect to see more of it, especially from smaller characters, and I'm fine with that.

I want spiders grappling giants.

Tiny House Spider rolls nat 20, gets 14. Kraken rolls nat 1, gets 11. Kraken now can't retreat back into the water because the itsy bitsy spider has caught its tentacle in its little web.

[pothocboots]

Tiny House Spider rolls nat 20, gets 14. Kraken rolls nat 1, gets 11. Kraken now can't retreat back into the water because the itsy bitsy spider has caught its tentacle in its little web.

Yes, good. Happens a bit more than 1 in 400.
Edit: Doing some math. There are 3 rolls the kraken can fail when the spider rolls 20.
2 when the spider rolls 19, 1 when the spider rolls 18. so 6/400
1.5% if ties go to the defender
2.5% if ties got to the attacker


This is what bounded accuracy was meant to maintain I thought. Even the smallest and weakest foe can still cause difficulties.
The kraken still has the option of killing the spider and then moving.

[Imbalance]

That time I was drunk at a toga party when the sky was spinning so I had to roll over and clutch the lawn with both hands to keep from falling off the world? I'm pretty sure I successfully grappled Earth. It's a shame there aren't mechanics to accurately represent that.

[Segev]

Yes, good. Happens a bit more than 1 in 400.
Edit: Doing some math. There are 3 rolls the kraken can fail when the spider rolls 20.
2 when the spider rolls 19, 1 when the spider rolls 18. so 6/400
1.5% if ties go to the defender
2.5% if ties got to the attacker


This is what bounded accuracy was meant to maintain I thought. Even the smallest and weakest foe can still cause difficulties.
The kraken still has the option of killing the spider and then moving.

Bounded accuracy is about maintaining relevance across levels more than across sizes. 5e is full of absolute cutoffs to close the gaps created by bounded accuracy.

Note, though, that I was mostly just finding amusement in that. I would expect that no DM is going to let the spider even roll, for the same reason that he doesn't feel the need to grant a DC 30 Strength (Athletics) check to let a bog standard human flap his arms and fly.

I'm also not saying that you should stick to the two size category difference max, if you don't want to. I'm all for it when you've got a believable narrative as to why it works. I was deliberately being ridiculous because it amused me. (That it also highlights a reason for the existing rules is a bonus, but not an argument that says the existing rules cannot be altered.)

[pothocboots]

I was deliberately being ridiculous because it amused me. (That it also highlights a reason for the existing rules is a bonus, but not an argument that says the existing rules cannot be altered.)

It amused me as well. And is a good illustration, I'll likely use it in future session zeros to help set what the tone should be.