An icy bridge problem. How long to melt ice, control water, and more.

[Odessa333]

Hey all,


so I'm run into a bit of a snag, and could use some help..


Set up: My players (Paladin, Fighter, Warlock, Cleric, Rogue, all level 9) are trying to cross a long bridge (120 feet). The bridge is iced over in an area of extreme cold. Their enemies knew they would have to cross here, and have set up an attack here, with a major rival archer set up to take advantage of the rough terrain. Making it worse, the area has magical high winds aiding the ambush, so flying and physical projectiles are impeded for the party, while the enemy sniper has the winds favoring their shots. This was designed to be the ideal conditions for a running antagonist, who chose this spot intentionally.


The complication: The players are looking for every way possible on how to get rid of the ice, willing to try and tank arrow shots while melting the ice. They want to know how thick the ice is, how long would it take to melt with torches / firebolt /prestidigitation / fireball / etc. One player is adamant that Control Water should work on ice to part the ice for them. Someone suggested using a gaseous form to get across, and I thought the high winds would impede that, but now I cannot find the ruling I thought I remembered for that.



Frankly, I have no bloody idea how thick ice gets on a bridge in extreme cold, or how long it would take to melt. I'm doing google search after search, and I'm striking out. I think the gaseous form would not work, and I am shutting down control water outright. Still, I'd love some advice / input from others on....well, any of this.


Thank you for your time.

[Amnestic]

How icy it'll get will depend on how much liquid's in the air, if it's been raining, and how much foot traffic, but I wouldn't complicate it overmuch with all that. Give the ice an HP amount (I'd say 5? Wall of Ice as 30, and that's 1 inch thick in 10ft sections) and vulnerability to fire (so 3 fire damage melts a 5ft square) and you're good to go. That'll take ~3 fireballs to clear up entirely, and that's probably their 'best' result. That seems like a pretty decent investment to make, considering they could otherwise just throw those three fireballs at the enemy instead.

I wouldn't let Prestidigitation work; that just 'warms' an object. Warming up ice isn't going to melt it within a combat timeframe.

Re: Gaseous Form, you might be thinking of specifically the Wind Wall spell, which states (among other things) "The strong wind keeps fog, smoke, and other gases at bay. Small or smaller flying creatures or objects can't pass through the wall. Loose, lightweight materials brought into the wall fly upward. Arrows, bolts, and other ordinary projectiles launched at targets behind the wall are deflected upward and automatically miss. (Boulders hurled by giants or siege engines, and similar projectiles, are unaffected.) Creatures in gaseous form can't pass through it."

The Warding Wind spell notably doesn't have this same clause, and only affects gas/fog that can be dispersed by strong winds - which gaseous form creatures cannot.

[da newt]

If you want to try to apply logic / realism:

W/ gaseous form you've got a 10' max speed (per 6 seconds = 100'/min = ~1.2 mph), so you can't overcome a breeze. (check my math)

In order to melt ice you need heat and TIME. Fireball is great for heat, but it has almost no dwell time, so it wouldn't melt much more than a thin surface layer (which would then refreeze pretty quickly if it's really cold there - arcane Zamboni).

Create Bonfire or fire wall or conjure fire elemental and some time - that would work, but sanding the surface would be much quicker / easier and plenty effective.

High winds make archery very difficult. The least effect is a shot directly into or with the wind. In order for one shooter to use this to his advantage, the target will also be shooting the reciprocal. Down wind will be faster and the arrow will hit higher than normal, up wind shots will be slower and hit lower than normal. But these ideals assume a steady wind parallel to the ground - shooting over a crevasse or whatever the bridge is over would likely create more complex winds with gusts and vectors in all 3 dimensions. Unless the expert archer has some magic on his side, he'll be just as effected as anyone.

Dimension Door would be their best bet, and waiting for darkness could help too.

[Slipjig]

Quick point of order: high winds should absolutely impede an archer, even if the wind is at his back. Wind doesn't fly perfectly straight, and firing even a few degrees off of true is going to introduce a significant cross-wind, which will make precision fire all but impossible.

That said, you can make the ice as thick as you want to. If it's been below freezing for an extended period and nobody has worked to keep the bridge clear, it could be several inches thick, and a momentary flash of heat from a Fireball may melt the top 1/8"... which just means that you now have a SLICKER surface, because now it's WET ice. Fire Bolt is going to melt something smaller than a saucer, which, again, will quickly refreeze.

[GooeyChewie]

Don’t try to estimate what would happen in real life. Even if you could, the players are trying melt it via magic means, which has no bearing on the real world. Besides, your players won’t have any idea what the ‘real’ answer ‘should’ be in the first place. The real question is how much of a challenge do you want to present to the players.

[elyktsorb]

Frankly, I have no bloody idea how thick ice gets on a bridge in extreme cold, or how long it would take to melt. I'm doing google search after search, and I'm striking out. I think the gaseous form would not work, and I am shutting down control water outright. Still, I'd love some advice / input from others on....well, any of this.


Thank you for your time.

Short answer, your not going to melt the ice on that bridge unless you set the whole thing on fire for a good few minutes, and even then it would certainly refreeze quickly. I guess if your players have access to a bunch of salt and a way to spread it over the bridge without putting themselves in direct danger that could work.

If I were your players, I'd just slide across it while prone. Or find another place to cross given there's a whole ambush waiting there. Or take advantage of the ice to upturn a cart, hide under it and slowly push it across the bridge from underneath it.

There are certainly options that don't involve having to get rid of the ice here.

[Odessa333]

Well, the 'good' news is that my players continue to plan on discord, and seem to be giving up on melting the ice.


The bad news is that they now want to turn their wagon upside down to make a covered 'sled.' They have plans on how to help push it with gust of wind, casting darkness on the sled, and letting the warlock with devil's sight steer.


I don't know where to begin figuring out the math on this one. Who knew one bridge would give me such trouble? Oy.

[Amnestic]

They have plans on how to help push it with gust of wind,

RAW this doesn't work; Gust of Wind only affects creatures and open flames, it wouldn't push an object.

Creating a movable barrier is a fine plan though.

[GooeyChewie]

Well, the 'good' news is that my players continue to plan on discord, and seem to be giving up on melting the ice.


The bad news is that they now want to turn their wagon upside down to make a covered 'sled.' They have plans on how to help push it with gust of wind, casting darkness on the sled, and letting the warlock with devil's sight steer.


I don't know where to begin figuring out the math on this one. Who knew one bridge would give me such trouble? Oy.

As with the ice, I would recommend not bothering with math at all. Instead, decide whether you want the plan to have a chance at success in the first place (as Amnestic mentioned by RAW it does not, but the DM can allow it). And if you want it to have a chance at success, do a skill challenge. Set up a series of plausible skill checks (Intelligence for setting the course, Strength for steadying the wagon, etc.) and if they succeed X times before they fail Y times, they get across. Usually you want three to seven successes prior to three failures, depending on how hard you want the skill challenge to be.

[Mastikator]

Wouldn't it make more sense for the rival archer to pour water on the bridge to make it slippery with ice. A slippery bridge plus a constant strong wind = people might fall of the bridge half way. The archer can then, from 600 feet away, snipe the ones that make it across

[Unoriginal]

Well, the 'good' news is that my players continue to plan on discord, and seem to be giving up on melting the ice.


The bad news is that they now want to turn their wagon upside down to make a covered 'sled.' They have plans on how to help push it with gust of wind, casting darkness on the sled, and letting the warlock with devil's sight steer.


I don't know where to begin figuring out the math on this one. Who knew one bridge would give me such trouble? Oy.

If the ice is that slippery, they can just push the upside-down wagon while they're under it.

[Segev]

I take it they can't cast fly, and hide in the lee of the bridge from the wind.

I know shape water can freeze water into ice; I am unsure if it can do the reverse, but even were it silent on that, I'd probably, as a DM, allow it. Not saying you have to if the spell doesn't say it works that way explicitly, though.

A creative use of control water would be to melt a little of the ice, then shape the water into a swirling tunnel across the top of the bridge. Whether it freezes or not, the controlled water isn't going to be pushed hard enough by the wind to knock it away (unless you rule it is, but I would expect anything that can hold tons of water up in a wall formation would be able to withstand winds that don't automatically sweep Medium creatures up into themselves).

Gust of wind could theoretically be used to push against the prevailing winds and create a dead zone either in its area or in a small lee around the caster, depending on how you want that to work, if you want to let it work.

The upside-down wagon could work, but what keeps it from being blown off the bridge? It's a lot of surface area. Maybe grappling hooks to "walk" it along, clinging to the side the wind is blowing from, so it can't go too far to the other side? Or walk along the side the wind is coming from and use poles to brace the wagon wall against the side of the bridge.

[Keravath]

Do the have crampons for walking on ice?

The party is pretty light on spellcasting so they likely don't have options like wall of fire or even firebolt unless it is a light cleric in which case they will have wall of fire which I suspect should do a decent job of melting ice considering it does 5d8 damage every 6 seconds.

You also don't mention how wide the bridge is, whether it has railings/sides and what the bridge is made out of.

The wind should definitely also affect the opposing archer unless you give them some magical arrows of ignore wind :)

However, even then, the archer is likely on the other side of the bridge so all the players need to do is take the bed of the wagon and use it as a moving wall in front of them as they carry it across the bridge that will give them somewhere between 3/4 and total cover from the archer.

Players can almost always come up with decent plans to mitigate ambushes if given the time and resources so it often isn't worth fighting it - just decide on how you want the combat to go.

For example, have any of the players looked under the bridge? A few innocuous bulges could turn out to be gargoyles or some other creature clinging to the bottom of the bridge. When the characters have passed, these creatures emerge and attack from behind while the archer puts some fire arrows into the wagon which the players may not realize until they smell the smoke.

Have a "pit" trap where the bridge floor drops away to allow creatures to plummet from the bridge. Of course, the bridge is designed such that wagon wheels are wide enough that they won't trigger any of the traps like this (this is useful in case they succeed in melting the ice or if the ice is only thick enough to make it a bit slippery and hide the trap doors - not thick enough to support weight).

Have the bridge be slightly uphill towards the far end and when the party is about 1/2 way across they see the opponents push a 15' spherical boulder onto the bridge (it rides on the short walls on either side of the walkway) and gains speed as it rolls towards them. Maybe using the wind behind it to accelerate the rock.

There are quite a few complications that you can introduce that would make sense and really aren't dependent on how the characters choose to cross the bridge. The characters are focusing on the obvious but aren't yet considering the likely but less obvious aspects of a clearly designed and planned ambush.

[Hairfish]

Don’t try to estimate what would happen in real life. Even if you could, the players are trying melt it via magic means, which has no bearing on the real world. Besides, your players won’t have any idea what the ‘real’ answer ‘should’ be in the first place. The real question is how much of a challenge do you want to present to the players.

Speaking as both a DM and someone who had to take a few classes on things like fluid physics and thermodynamics and can actually calculate this stuff, I absolutely agree with this poster. You're the group leader in an attempt to tell a story that you all find engaging, not apply RL science to an imaginary world where people can speak a word to shoot fire from their fingers and get to run 30' and swing a sword at an orc without the orc simultaneously trying to close the distance and swing an axe at them (or vice-versa, if the orc rolled higher initiative).

Let literally anything they try potentially work, unless it's absolutely the dumbest **** you've ever heard of. Figure out a skill/proficiency check for whatever they're trying to do and have them roll for it. Is it kinda dumb and/or boring? Impose disadvantage. Is it smart and/or awesome? Grant advantage.

[Odessa333]

I know/get the whole 'You're the DM, you decide' etc stuff. As to the science comments, at no point do I try to calculate the energy needed to cut through an orc's armor, or question the fall damage the game uses. Still, when something I don't know comes up - like what spells melt ice - I do try to do my research, figure out how that kind of thing could work. It makes me smarter as a person, and helps keep the game logically consistent, that I'm not changing my mind or ret-conning things later.


For example, I shut down the 'ice is cold water, and it counts as free standing water, so I can part the ice' as I KNOW my players, and if I did THAT, they'd be screwing around with 'hot water' and trying to combine the whirlpool effect with water vapor to make a tornado or something worse. Which would be cool the first time they did it, but I have no idea how I'd balance the party just tossing tornado's everywhere they went.


On the flip side, due to some magic hijinks, they found a way to drop a 300 pound object onto a major villain. I didn't stop the game to run the math, that person was just dead. They thought of something clever that worked with the given rules, and that should be encouraged.



I think of it akin to something my old writing teacher used to say: you need to know what the rules are before you can deliberately break them.



If the above was happening in real time during play, I would take a minute (at most) to try and google some examples, then wing it. As they are planning for next week's session over discord, it gives me more time to make a post (like this one...) and do more research.

Hopefully that makes some sense.

[da newt]

Is this a natural bridge or did some group of people design and build it? It's the only way across for a significant distance along a route of some use/importance, right? The winds and cold here are common occurrences, right?

The bridge ought to have been built so that commoners and trade can regularly move across it safely (horse drawn carts, etc). It should be significantly wide, flat, and have railings that protect against slipping off.

Unless of course this is the entrance to a fortified location that has been designed as an easily defended choke point ...


Bottom line, I'd suggest letting your PCs feel like they have been clever and succeeded in out thinking your trap, then adjust as necessary to add a bit of risk / cost so they really feel like they accomplished something.