Need a little help DMing an odd combat mechanic

[mentalorigami]

I'm DMing a campaign soon and I want to make their first big combat encounter a little more fun than the standard four or five skeletons and a zombie kind of thing.

The start of the adventure takes place on a large merchant ship (about 30 tiles long and 8 wide, 4 main decks; top, galley, berths, and a cargo hold) which is being boarded by some baddies, and I want to put a sense of urgency into the combat by having the ship lit on fire in multiple places. There will be buckets of sand scattered about the vessel so that players can put out a limited amount of fire (to access treasure stored on board or rescue an NPC or two) but ultimately I want the whole thing is going to burn down to the water line, or be totally unusable as a ship.

So my idea is to have the every fire tile spread outward after a certain number of turns, engulfing whatever is in its path while the combat rages on (and it will, the supply of baddies will be nearly endless till they disembark). The idea was once every 30 or 35 rounds, but I'm having second thoughts now on the timing. I want to make it impossible for them to put out the fire completely, but not so difficult that they can't do some looting/heroics before they have to jump ship.

Does anyone have any advice here? I want to keep it fun without having to fudge it too much, or take too much time away from combat spreading the flames, but I'm worried my PCs won't have enough common sense to free the right people (not that the story hinges on that, but certain NPCs would help them later on) or get to the lifeboats in time.

As an addendum, how likely would a large merchant vessel have folding boats? I was thinking of keeping one in the captains quarters as a nice getaway vehicle, but at 7k gold it seems much to expensive and exotic for a common merchant.
So, what do?

[Vhaidara]

First, what is the composition of you party? 30 rounds is insanely long. I think the longest encounter I've ever had was 7. If you have any casters, they will be completely out of spells relatively quickly.

[mentalorigami]

Ranger, druid, fighter, sorcerer, bard, probably.. they're still deciding. The enemies are going to be under-leveled for them, easy to one or two shot, but numerous, so combat will hopefully move very quickly.

30 rounds maybe a bit much.. but I figured fire would spread about 5 or 10 feet every few minutes, so 5ft per 3min (6 seconds a round @ 30 rounds, 180 seconds, 3 min) would be adequate without being overwhelming.

[Blackhawk748]

While that may be true for real life, i have never had a combat encounter that lasted that long, the longest boss fight i've ever had was about 15 rounds, most of our combats are usually over in about 1-5 rounds. Now you are doing wave tactics so the fight can go on for a long time, but id prbly have the fire spread every 5 or 10 rounds instead of 30, remember your on a ship and if fire started it could easily have hit the lamp oil.

[Vhaidara]

Also, what level will your players be? That druid could run your day by preparing 1 Create Water. 0 level spell making 2 gallons per caster level.

Also, fire actually spreads pretty fast. I forget the exact number, but it came up in a recent thread that a building can be completely aflame within like 10 minutes.

[ericgrau]

The last time this came up I think I read that fires take a few minutes to spread : too slow to worry about in combat, too fast to reach the next fight. IIRC it wouldn't even spread 1 square in your typical 5 round fight, or barely 1 square. But in ~10 minutes the ship is fully engulfed.

Because fires spread faster and faster, you either catch it early and extinguish the whole thing, or catch it late and it spreads faster than you put it out making your efforts pointless. If you limit the amount of sand to less than the starting fire size you could let the players make some progress but ultimately fail when the sand runs out. They might still use canvas to smother the fire and/or spells though in spite of the sand limit. If they're clever I wouldn't railroad them; let the ship survive.

From what I googled I think 2 gallons of water puts out a fire in 1 square if used efficiently. But more likely after putting out a fire a couple gallons may stay in the same square and temporarily prevent future fire until it dries up, rather than spreading to an adjacent square. As a guess say 2 gallons of extinguishing plus 2 gallons of prevention on each square.

As a guess you might have fire spread to all adjacent squares every 2 minutes, and diagonally every 3 minutes. Larger fires may spread faster, so have the fully surrounded squares reduce this time: once you hit about a 15 foot radius maybe to 1 minute and 1.5 minutes, and half as long again once it's 30 foot radius, etc. And for some total BS that I haven't looked up at all, just say a large bag of sand puts out 1 square, takes a move action to pick up and a full round action to dump.

[Blackhawk748]

Also, fire actually spreads pretty fast. I forget the exact number, but it came up in a recent thread that a building can be completely aflame within like 10 minutes.

I remember this thread, it was a discussion about making fire more threatening, and rules for smoke inhalation and whatnot. Oh btw use that if they are in the hold.

and i agree with ericgrau for the snad mechanics, nice and simple

[mentalorigami]

Ahh good point with the druid's create water spell. They're going to be level 5 coming into this, I'll have to figure something out with her. Though I'd probably rule that just two gallons of water raining down can't put out a raging 5'x5' fire on a ship.. maybe the heat would evaporate most of it before it could smother the flame.. will have to think about that. Ten gallons would be another story though. The hope is they have no idea the whole ship will be aflame, and not prepare that spell, as food and clean water is easy to come by on a merchant ship. Can't predict the players though.

Agreed on the lamp oil. But now that gives me mischievous ideas about having exploding caches of lamp oil.

So now that I'm thinking about it, cutting the spread down to 5-10 rounds might achieve what I'm looking for, especially combined with some "mishaps" with lamp oil and gun powder. I really want to keep the tension high.

Forgot to mention, the ship's doomed no matter what, it runs aground on a rocky shoal right before the fight, effectively disabling the ship and punching a series of small holes in the forward stowage while keeping it above water for a few hours. Slow leak, but ultimately doomed. The idea is that the captain was lured into the shoal by a mysterious force, think ye-oldy LOST. Party has to escape their ship, find land, and kill what's causing the shipwrecks, before they can escape completely. It's a little railroaded, but we're doing a DM rotation and I wanted a fun, one off scenario that wouldn't get out of hand and run on forever.

[Blackhawk748]

Well as far as railroads go, thats a short branch line to the destination, also its an entirely plausible so yay for that.

Oh dont forget that water will not put out an oil fire, so be sure to remember what fire is caused by what.

[ericgrau]

Well actually water is not good for putting out oil fires because it makes the oil spread. It will still put out the fire... but possibly cause even more fire until the oil is used up.

A pint of oil is good for 2 rounds on a square or 6 hours in a lantern. 8 pints in a gallon, 320 in a 40 gallon barrel. The lantern number is to figure out how much oil they might need to carry on-board.

I'd guess a burst barrel might cover 10 squares leading to 64 rounds of burning. But water could make that into more squares at a shorter duration.

Gunpowder can burn without air so it is likely to be used up all at once or very quickly for a big but brief flare. Oil is slower because the airless oil underneath needs to wait for the oil on top. Even when it is only a fraction of an inch thick. Also why spreading oil does bad things.

[arkangel111]

I would have the fires double in size every round. perhaps adding a fire every 3rd round. For instance on round one you have 5 fires all in separate 5ft squares (I would space them out far enough that the PC's can't get to them all in one round). The PC's think its all for show and they can deal with it later and instead wade into combat. Round 2 the PC's continue to fight, again thinking the fires are just for show, but at the bottom of the initiative you double them all. Giving you 5 fires at 2 squares each.

I would let your sand idea take a standard action to remove 1 square or a full round to either halt the progress or to remove 2 squares, so they would be able to stay ahead of the fires, since the fires go last (i would follow normal rules for create water, or if there are none I would have it follow these), whatever your rule set be sure to let the PC's know all their options the moment they grab the sand or create water.

On round 3 the PC's split up to do fire duty, and 2 of them decide to sand some fires while the others fight. Since its round 3 you add a 5 ft square (perhaps a fire arrow just landed on the deck) and then you have your remaining fires. 3 @ 2 squares ea. which then change to 4 each. and your 2 @ 1 square ea. which then change to to 2 squares. For a grand total of 17 squares on your 240 square deck

By round 4 combat might be wrapping up, so you may need to throw in some reserves, nothing to kill them of course but enough to continue to draw at least 1-2 PC's from fire duty. Although your 4 square fires are nearly out of control changing to 8 squares each at the end of the round, barring PC intervention. The PC's should start feeling the urgency of this fire and a few may even have the idea to look for a way out. Either way, one of the largest commodities on a merchant ship is gonna be some form of alcohol, I like rum (bonus points for having the merchant captain or the zombie leader be named Morgan). Alcohol is known for its violent reaction with fire so, at least a fireball sized explosion could happen, adding fires as needed to let your PC's know that the ship is gonna go down either way and they need a way off the boat. (I would try to save the explosion for either when the PC's think they are winning, or if they are failing to act the way you desire, so not necessarily in round 4)

Anyways the above is just a suggestion. One thing to keep in mind is 5 minds always think better than one so you may need to add more than 1 fire every 3 rounds if your PC's are putting out your fires too easily. Perhaps 1/2 rnds or 3/3 rnds.

As for the folding boat that might be a bit much however I believe there is a quall's feather token boat that only lasts 1 day and is waaay cheaper.

[ericgrau]

I'll also leave this here: http://www.d20srd.org/srd/environment.htm#catchingOnFire . The smoke section is relevant for anyone deep in a fire too, or in an enclosed room.

And I think somewhere in the oil rules it says standing in an area of fire without being caught on fire does 1d3 damage. I don't think this stacks with being caught on fire.

[mentalorigami]

You guys bring up some great points here. Smoke isn't going to be an issue unless they venture into stowage, but the possibilities of explosions down there will be well know to them. Hopefully it will be a nice risk vs reward. I planned on letting them have a little tour of the ship the day before the big combat encounter to set the back story and make sure their characters know where all the goodies and hazards are stashed. Then they go to sleep at night (hopefully..) and are woken up by the jolt of the ship hitting the shoal.

The sand is definitely going to take a full round action to spread. My idea was a 25lb bucket (20lbs of sand in a 5lb wooden bucket), can only take move actions at half your base speed per round while holding the bucket, pick up/pass/put down the bucket as a standard action, or any free actions that don't require the use of your hands. Requires the use of both hands to keep from spilling, no crossbow wielding, bucket slinging PCs. Must be adjacent to the fire you want to put out. Any fire spreading to a tile with a PC on it causes them to drop the sand and put the fire out, but they can only take a move action on their next turn.

Arkangel, that's a good idea with the doubling, I'm going to play test it a little and see which method I want to use. Increasingly leaning towards a much shorter (probably 5 round) spread time to keep things interesting.

Had a new thought though. As the ship is quite large, 150ft of deck space from bow to stern, having the fire spreading in an area the PCs have not yet visited seems a little unfair. My thought was once the fire is in their line of sight it starts to spread, but never before. That way in case they don't make it to the stern where the captains cabin is located within the requisite number of rounds it won't be totally burned to a crisp. Having loot or NPCs vanish without any chance of retrieval by the PCs seems too harsh for a new mechanic like this. Though if they run past a room with smoke coming out the door and they do nothing about it I won't help them at all. What do you guys think?

[hemming]

Well, I edited some out that doesn't apply here but if I may regurgitate my post on fire from another thread:

The ship fire rules from stormwrack (p31) could be of use:

-Entering a burning square does 2D6 dam and must make DC 15 reflex save or catch fire (taking an additional 1D6 that round and each subsequent round until save is made per DMG) - so traveling through 30 ft of burning squares is 12D6 dam no save + 6 reflex saves or catch fire

-Each turn roll d%: 1-10 = 1 square burns out ; 11-75 = no change; 76-100 = fire spreads by one square per 4 on fire

DMG-

-Smoke Effects (DMG p304) - Fort save each round (DC15+1 per previous check) or spend round choking and coughing (no action); choke for two rounds and take 1D6 nonlethal

-Extreme Heat (p303) - (if air temp is 140 F or higher) 1d6 dam per minute (no save); Fort save (15 + 1 per previous) or take 1D4/round. Any armor gives you a -4 to save; all metal items act as though affected by a heat metal spell

Substitute search for spot checks to fit the situation better and:

-You could treat weakened sections of floor as concealed 10 foot deep pit traps (Ref to avoid; maybe with an added pinned by rubble or burning rubble effect)

-treat falling beams as "Stone blocks from ceiling" traps (search DC 25) with 2d6 physical dam and 2d6 burning dam

-obviously the party won't be able to disable these 'traps' through conventional means

Edit: how much you want a sense of urgency in dealing with the fire is going to have to do mostly with the initial size of the fire and number of source if you decide to use the stormwrack rules - The rules for fire spreading are based on each 10x10 section of the ship (not by each 5' square)

[mentalorigami]

-Each turn roll d%: 1-10 = 1 square burns out ; 11-75 = no change; 76-100 = fire spreads by one square per 4 on fire

...

-You could treat weakened sections of floor as concealed 10 foot deep pit traps (Ref to avoid; maybe with an added pinned by rubble or burning rubble effect)

...


I like these ideas a lot, but I think with a large ship and a lot of fire rolling the d% for each one would get out of hand very quickly, even with 10'x10' sections. Keeping the tension high in combat also means (at least to me) keeping it moving with as few interruptions as possible, and just spreading all the fire each time around makes it a lot faster.

I am definitely going to keep the weakened sections as pit fall traps. Maybe any section that was previously, or is on fire is weakened, d%: 1-x to trigger where x is the character's total weight divided by 4 or 5? That way the chance is somewhat low for light PCs, but a heavy PC has to tread lightly (so the dwarf warrior with 150lbs of gear and fatness can't sprint across the burned sections with impunity). DC 15 reflex save to avoid, jumping back to the last tile you were on. Failure means falling down to the deck below, taking 1d6 points of damage and probably falling to an inferno.

[3WhiteFox3]

Create water is 10 gallons at level 5. Also, while an oil fire can spread with water, from what I've read that's only if you don't use enough water to extinguish the flames completely. I'm no firefighter so I'm not entirely sure, but that's what I've read.

[hemming]

I like these ideas a lot, but I think with a large ship and a lot of fire rolling the d% for each one would get out of hand very quickly, even with 10'x10' sections. Keeping the tension high in combat also means (at least to me) keeping it moving with as few interruptions as possible, and just spreading all the fire each time around makes it a lot faster.

You would roll for each "fire" - so if 8 sections are on fire and you roll an 86, the fire spreads to 2 more squares sections

However, this doesn't give you the narrative ability as a DM to have the fire where you want it, when you want it (at least not without playing out a bunch of 'fire spreading' scenarios ahead of time to get a feel for it). And it is definitely more cumbersome than narrating the life of the fire (as you point out)

You could also have "firebombs" (barrels full of alchemist fire used in naval combat) in the way of the fire or as the initial source - explosions are cool and can help you kick up the urgency in a key moment