So. I'm not even sure if I'm posting in the proper forum, but here goes.

I'm playing a Druid, but this is a question about Caltrops.

I've been trying to wrap my head around how this would work.
Say, I'm in the jungle and I have a bag of 20 caltrops.
Is that enough to cover a 5' square?
How would the mechanics of the attack happen and how much damage could they do?

I'm trying to determine if this would be worth my time in the earlier rounds.
I'm contemplating different types of caltrops (wooden, metallic, glass) depending on the surface.
I'm also mulling if dipping them in poison or some other liquid could make them extra nasty.
If the damage numbers are too low, I'd probably just ditch the idea altogether, but I'm trying to stay true to the character, who is a survivalist type of Druid (think Rambo).
Building traps, making spikes and homemade caltrops are all part of his routine.

Any thoughts or ideas would be helpful.  I'm trying to push the boundaries of what could be done with simple equipment items, before the melee rounds kick in.

Thanks for the input.

 Caltrops do very little damage. However anyone who does get hit by them has their movement speed reduced, which is their main value. They're extremely useful if there's a choke point that your enemies will have to March through. There's no rules that I know of for how they would work if coated in poison, but I don't see why that wouldn't work if you used the right poison.

"As an action, you can spread a bag of caltrops to cover a square area that is 5 feet on a side. Any creature that enters the area must succeed on a DC 15 Dexterity saving throw or stop moving this turn and take 1 piercing damage. Taking this damage reduces the creature's walking speed by 10 feet until the creature regains at least 1 hit point. A creature moving through the area at half speed doesn't need to make the save."

One bag of 20 caltrops is considered enough to trap a single five-foot square, A.K.A. a Standard D&D Combat Space.  Any creature that moves into that space without treating it as difficult terrain (i.e. consuming twice the movement to get through it, which is mechanically equivalent to moving at half speed) has to make a DC 15 Dex save.  If they flub it, they take one piercing damage, stop moving, and have to heal themselves to regain the lost movement.  That's how they work.  The mechanics of it are very straightforward.  There's no attack involved, and the damage from the caltrops is, RAW, never higher than one.  They're a hindrance and an area denial tool, not a damage option.

What is highly, highly worth noting is that there is no line stating that the speed reduction only happens once.  If you have multiple sets of caltrops and trap a wide area (or if the creature is somehow stupid enough to hit the same set more than once), a creature that hits three or more sets is now reduced to zero speed until it heals.  Every time it takes that one lousy point of piercing damage, it loses speed.

Soaking the caltrops in poison would be up to the DM.  Speaking from my DM mode, I wouldn't see any reason not to allow someone to treat a bag of caltrops with poison, though the mechanics of how that would work would have to be discussed, and would probably end up a little game-y.  Caltrops made from weaker materials, i.e. wood, likely wouldn't work well against any target wearing decent footwear. 

Caltrops made of glass are a war crime and you should feel awful for even suggesting it what is wrong with you sir WHAT IS WRONG WITH YOU DX

As for whether it's worth your time?  Depends on how often you have time to set up caltrops, and how often making one single Standard Combat Space an awful place to be is worthwhile.  Personally, my players tend to try and have some caltrops with them whenever they can, though obtaining them is usually a crafting check rather than just a straight purchase.  Regular rural villagers tend to get suspicious when adventurers start asking for shady shit like caltrops.  Sophisticated cityfolk merchant-types tend to get even more suspicious, unless they've met adventurers before and are aware of how bizarre and awkwardly paranoid most of them are.

My logic was to use different types of caltrops, dependent upon the surface of the area.

Glass Caltrops (made by a glassblower) - I was thinking these might work well in a smooth tile/stone type of setting.

Wooden Caltrops - Typically indoor dwellings, staircases, tight corners, dimly lit hallways.

Metal Caltrops - Outdoors, high traffic creatures/animals, horse carts, caravans, etc.

It's good to know that their main focus is to reduce speed or cause some sort of disadvantage.
That changes my mindset. Initially, I was thinking that they could be a good way to cause that initial damage before range attacks and melee action.
My character doesn't do much tank-y type of stuff, so I'm trying to think of useful ways he can contribute (knocking prone, causing disadvantage, rough terrain)

He's a survivalist type and frequently uses Mold Earth / Shape Water to create scenarios.
Pits/Traps/Rough Terrain are his thing.

Functionally there's no difference in caltrops based on what they're made out of. They're assumed to be made of metal. Mostly it's just a question of if you can craft them yourself or not. Depending on your DM, they might let you craft them using wood carving tools. But based on what you said about your character... You could do well adding caltrops to your bag of tricks

Caltrops could also theoretically be napped from some sort of stone like slate or obsidian (volcanic glass). Most children I know use LEGOs though.😂

I would also like to point out to be wary of scattering them around during combat. Depending on the intelligence of the enemy, they'll simply see you spreading them out, look at you weirdly then either completely avoid the area or intentionally walk at half speed completely ignoring you. They're meant as traps and hindrances. You wouldn't start digging a pit trap in front of the target either.

When you know you're expecting company, your ranged attackers hunker down behind cover but litter the entire area heading towards you in caltrops giving you guys an extra turn (or more) until they reach you.

Also consider ball bearings. Instead of the 1 piercing damage + speed reduction, anyone running through the area needs to make a dex save or fall prone. These are best in chases or 'baits' when you run through a doorway or hallway, have an enemy chase you and your ally throws them behind you, tripping them.

But remember, these are pretty obvious when throwing them out in full view of the enemy. A half smart enemy will know what they are. Kobold description deliberately say that they use traps so they should be very familiar with them. Even a brain dead enemy would be curious at those 'shiny metal stuff' you threw on the ground, warily walk up to it, sniff it, realize that it's pointy and avoid it. At worse, the DM may make a really low INT check.

Druid is a great take on a survivalist, but question, why don't you just go ranger? They literally ARE the survivor/navigators/Rambos

As a DM I'd say caltrops don't work in a jungle.  Unless you're assuming all different environments are actually not different. ...or you're in a part of a jungle where the ground is flat and hard without many layers of leaves, branches, or soft and highly degraded plant material....so in a part of the jungle that isn't jungle.

I could see them working in jungle. Part of the point of caltrops is they're designed so that no matter how they land, there's always one extremely pointy bit sticking up (much like d4s...) Yes, they'll sink into soft jungle dirt to a point, but if the ground is solid enough to walk on, they're still going to jab you in the feet. Mud might actually be worse - the mud would just hide them, making them MUCH harder to see, and then they slash up your muddy feet.

Punji sticks are a thing.  You don't exactly carry around bags of punji sticks, but I'd argue that if you have a spare hour, you could set up punji sticks in a 'Jungle' tile/Standard Combat Space and they'd act the same as caltrops.  Plus side, you can source the sticks from materials local to the area and don't need to carry them around with you.

Quote from Yurei1453 >>

Punji sticks are a thing.  You don't exactly carry around bags of punji sticks, but I'd argue that if you have a spare hour, you could set up punji sticks in a 'Jungle' tile/Standard Combat Space and they'd act the same as caltrops.  Plus side, you can source the sticks from materials local to the area and don't need to carry them around with you.

 think that's a spiked pit trap

Please note that multiple rounds of caltrop damage would not continue to reduce speed by 10 feet down to 0, though they would reapply their 1 damage and stop moving for that turn effects. See DMG Chapter 8: Running the Game - Combining Game Effects. While the list provided of game features to which this applies is stated as "spells, class features, feats, racial traits, monster abilities, and magic items," the absence of "other special items" is probably not going to get you very far with your DM when you try to argue that three rounds of caltrops cripples an opponent. 

Quote from Yurei1453>>

What is highly, highly worth noting is that there is no line stating that the speed reduction only happens once.  If you have multiple sets of caltrops and trap a wide area (or if the creature is somehow stupid enough to hit the same set more than once), a creature that hits three or more sets is now reduced to zero speed until it heals.  Every time it takes that one lousy point of piercing damage, it loses speed.

This isn't correct. As DMG chapter 8 points out (Combat, Combining Game Effects), two instances of a game feature with the same name don't stack. A humanoid isn't going to become immobile just because their foot now has three tiny holes instead of one.

Fair enough, my mistake.

Nevertheless, I would contend that properly emplaced caltrops could be very useful, especially for a druid who can take other speed-reducing effects into play, such as Ray of Frost.  It's not an every-fight thing, but it's definitely something worth having in your bag of tricks.

If a creature tried to jump over caltrops and the landing area was covered in ball bearings, I think I would impose disadvantage on the saving throw just because describing the creature’s landing would be hilarious.

Or, put some very visible caltrops in one square, and then some hidden caltrops in the next so that they leap into them? The save/damage/conditions on a bag of caltrops are appropriate for a creature that walks/runs onto them, but as a DM I'd probably be willing to houserule to enhance them a little for someone leaping or falling onto them (no save or a harder save to avoid? or, 1d4 damage instead of 1?)

Quote from Trirhabda >>

If a creature tried to jump over caltrops and the landing area was covered in ball bearings, I think I would impose disadvantage on the saving throw just because describing the creature’s landing would be hilarious.

 its a jungle...i'd say ball bearings would be even less effective than caltrops.  go throw a bunch of marbles in your yard (let alone a jungle floor) and walk over them...see if you slip. you can even give yourself disadvantage with a beer in each hand and a burger wedged in your mouth...and you still won't slip.

character throws a bag of ball bearings on a jungle floor and this DM will be like 'you look around and realize you lost your bag of ball bearings. you curse the heavens.'

Quote from HeathSmith >>

As a DM I'd say caltrops don't work in a jungle.  Unless you're assuming all different environments are actually not different. ...or you're in a part of a jungle where the ground is flat and hard without many layers of leaves, branches, or soft and highly degraded plant material....so in a part of the jungle that isn't jungle.

 Caltrops would work in a jungle. Pointy things are pointy even if they are on dirt or grass.

Ball bearings do require a flat surface though.