HD&D: Temperature Extremes

The Dungeons and Dragons rules are a complicated tapestry. For one set of rules to make sense, we need to understand another set of rules. And so it was, while I was considering underwater combat, that I discovered I needed rules on what happens to a body when it suffers extremes of temperature. After all, it gets cold in the deep ocean.

Now there’s no point in having two sets of rules for temperature extremes (one for water and one for dry land) so I looked at the problem as a whole and came up with the following rules. Those who own the third edition books will see that these rules are heavily inspired by the most excellent Frostburn and Sandstorm sourcebooks. I think they speak for themselves, so I’ll dispense with the preamble and just get on with it:

Protection Against Extremes of Temperature

Adventurers  often find themselves into all manner of dangerous situations. They might be challenged by a barbarian tribe to spend a night on the Great Glacier wearing only their underpants, they might bungee jump into an active volcano to recover a treasured childhood toy, or they might find themselves teleported into the middle of an arid desert without parasol or sun-tan lotion. It these circumstances, it is the environment and not the vicious monsters that live there that pose a threat to your character.

Creatures protect themselves against extremes of temperature by their equipment, spells, feats as well as their intrinsic biological advantages. Levels of protection against Cold and Heat dangers are measured on a scale of 0 to 5, where 0 is the least protected and 5 is the most protected. This level of protection is then compared to the effects of a temperature band to determine the effects of temperature on a character. Here’s what you need for the base levels of protection:

Base Description
0 Creature has no temperature adaptation 
1 Cold or Heat Endurance Feat
Creatures is native or a Cold of Hot terrain
 
2 Particularly cold-tolerant character
Creature native to an area of Severe Cold or Severe Heat.
3 Creature has Resist Cold 5 or Resist Fire 5 

In addition to the base level of protection, certain items of equipment can apply bonuses to your level of protection. These bonuses do not stack with one another unless the text explicitly says so. Here here are the most common items that can help you avoid extremes of temperature:

Armourbright: This metallic paint is applied with a brush to the outside of a suit of armor (requiring 1 minute to apply), producing a shiny surface that reflects the light of the sun to reduce the effects of hot weather on the wearer. For 24 hours after applying armorbright to a suit of armor, you gain a +2 bonus to your Fortitude Defence against heat dangers (including heatstroke).

Armorbright provides a +1 bonus to your level of protection against Heat dangers. However, it is not effective in hot environments with no sun, such as the Elemental Plane of Fire.

Armour Insulation: This thick red syrupy mixture is applied with a brush to the inner surface of a suit of armor. When the mixture comes in contact with body heat and sweat, it puffs up to trap body heat, insulating the wearer against the effects of cold. For 24 hours after application, the wearer of a suit of armor treated with armor insulation gains a +5 circumstance bonus to your Fortitude Defence against exposure to cold weather, and a -5 penalty to their Fortitude Defence against exposure to hot weather (incuding hypothermia and heatstroke respectively).

Armour insultation provides a +1 bonus to your level of protection against Cold dangers, and a -1 penalty to your level of protection against Heat dangers. This bonus stacks with fur clothing, but not with a cold weather outfit or an improvised shelter.

Cold Weather Outfit: A cold weather outfit includes a wool coat, linen shirt, wool cap, heavy cloak, thick pants or skirt, and boots. This outfit grants a +5 circumstance to your Fortitude Defence against exposure to cold weather, and a -5 penalty to your Fortitude Defence against exposure to hot weather (incuding hypothermia and heatstroke respectively).

A cold weather outfit provides a +1 bonus to your level of protection against Cold dangers, and a -1 penalty to your level of protection against Heat dangers. This bonus stacks with fur clothing, but not with a armour insulation or an improvised shelter.

Desert Outfit: This outfit consists of loose, billowy clothing to keep the wearer cool and protected from the sun while in hot, dry desert terrain. It includes a caftan, turban, scarf, loose pantaloons, and sandals or high cloth boots.

A desert outfit provides a +1 bonus to your level of protection against Heat dangers. The protection it offers against heat is negated if the wearer also dons armor.

Fur Clothing: Fur clothing consists of thick layers of animal furs designed to be worn over a regular set of clothing or armour. Wearing fur clothing grants a +5 circumstance bonus to your Fortitude Defence against exposure to cold weather; and a -5 penalty to your Fortitude Defence against exposure to hot weather (incuding hypothermia and heatstroke respectively). Fur clothing is cumbersome to wear. Although the furs do not provide an appreciable armor bonus, they do give you a 2 point armour check penalty. This penalty stacks with any armour you are wearing.

Fur clothing provides a +1 bonus to your level of protection against Cold dangers, and a -1 penalty to your level of protection against Heat dangers. This bonus stacks either armour insulation or a cold weater outfit, but not both. It does not stack with the bonus gained from an improvised shelter.

Heat Suit: This suit is designed to protect against heat. It consists of heavy pants and coat, a specially treated leather apron, thick mittens, a thick hood, and goggles. Wearing a heat suit grants a +5 circumstances bonus to your Fortitude defence against heat dangers (incuding heatstroke).

A heat suit provides a +1 bonus on your level of protection against heat dangers.

Hydration Suit: The hydration suit is a masterpiece of water retention, crafted by desert-dwellers with technical skill and unusual materials. Its design allows you to recover nearly all the water your body loses through sweat, exhalation and excretion. A hydration suit is made of the skin and tissue of various desert-dwelling beasts and treated with oils or waxes for water retention. It covers your entire body, with a tight-fitting hood over the head and a mask covering the mouth and nose. Inside the mask is a glass plate to collect condensation and a tube fashioned from watertight materials. An inner lining wicks sweat away from your body and collects it in spongelike filtration material that can be removed after you doff the hydration suit. The tube from the facemask twists in loops around your body, through the sponge, to reclaim moisture, condensing it in a reservoir from which you can sip.

A hydration suit provides a +2 bonus on your level of protection against heat dangers. It offers significant protection against dehydration (see below).

Improvised Shelter: An improvised shelter is any structure, windbreak or shade that grants you protection against the prevailing environmental conditions. It might be a portable hut, a snow hole, a deep cave or even a thick copse of hardy trees. Improvised shelters increase your level of protection by +3 against both heat and cold dangers.

Temperature Bands

All Hot and Cold environments fall into one of the twelve temperature bands listed in the table below. Your level of protection (as noted above) is compared with the effects at a certain temperature band to determine the deliterious effects to your character (if any).

The levels of protection only offer protection over the range of temperatures from Unearthly Cold to Unearthly Heat. They are useless in areas of Freezing Cold or Burning Heat. Characters with Resist Cold 10 can withstand all temperatures down to Unearthly Cold with no protection at all. Equally, characters with Resist Fire 10 can withstand all temperatures up to Unearthly Heat. Resist 15 is required to escape either Freezing Cold or Burning Heat without damage.

Fahrenhite Celsius Band
-81°F or lower -63° to lower Freezing Cold
-51°F to -80°F -46°C to -62°C Unearthly Cold
-21°F to -50°F  -29°C to -45°C Extreme Cold
0°F to -20°F -18°C to -28°C Severe Cold
1°F to 40°F -17°C to 4°C Cold
41°F to 60°F 5°C to 15°C Moderate
61°F to 90°F 16°C to 32°C Warm
91°F to 110°F 33°C to 43°C Hot
111°F to 140°F  44°C to 60°C Severe Heat
141°F to 180°F 61°C to 82°C Extreme Heat
181°F to 210°F 83°C to 99°C Unearthly Heat
211°F or higher 100°C or higher Burning Heat

Freezing Cold: Only supernatural environments ever get as cold as this. Stepping out into such terrible cold is enough to flash-freeze a living creatures in moments.  In a region in this temperature band, characters take 15 points of lethal cold damage per round. In addition, those wearing metal armour or coming into contact with very cold metal are affected as if by a chill metal (q.v.) spell (which lasts as long as the character remains in the area of freezing). Generally, mundane methods of protection against heat offer no protection in areas of burning heat, and various levels of heat protection are meaningless unless it is immune or highly resistant to cold. Characters at this temperature automatically contract hypothermia on their first round of exposure.

Unearthly Cold: Unprotected characters take 10 points of lethal cold damage, and 10 points of subdual cold damage, per minute (10 rounds). The damage is inflicted in phase one of the tenth round. Every time a character takes damage (but no more than once per round), the GM must make an attack roll agains the character’s Fortitude Defence to see if that character has contracted Hypothermia (q.v.). Those wearing metal armour or coming into contact with very cold metal are affected as if by a chill metal (q.v.) spell. Partially protected characters take damage once per 10 minutes instead of once per minute. For complete protection against the effects of unearthly cold, a character must have a level of protection of 4 or higher. Level 2 or 3 is considered partial protection, and level 1 is no protection at all. Liquids carried by characters will almost certainly freeze solid.

Extreme Cold: Unprotected characters take 5 points of lethal cold damage, and 5 points of subdual cold damage, every ten minutes (100 rounds). The damage is inflicted in phase one of the one hundedth round.  Every time a character takes damage (but no more than once per round), the GM must make an attack roll agains the character’s Fortitude Defence to see if that character has contracted Hypothermia (q.v.). Those wearing metal armour or coming into contact with very cold metal are affected as if by a chill metal (q.v.) spell. A partially protected character takes damage once per hour instead of once per 10 minutes. A character must have a level of protection of 3 or higher to be protected against extreme cold. Level 2 is considered partial protection; level 1 is considered unprotected. Liquids carried by characters will almost certainly freeze solid.

Severe Cold: Unprotected characters must make a Fortitude save every 10 minutes (DC 15, +1 per previous check), or take 5 points of cold subdual damage on each failed save. A partially protected character need only check once per hour. Every time a character takes damage (but no more than once per round), the GM must make an attack roll agains the character’s Fortitude Defence to see if that character has contracted Hypothermia (q.v.).  For complete protection against severe cold, a character must have a level of protection of 2 or higher. A character whose level of protection is only 1 is considered partially protected. Liquids carried by characters will probably have frozen solid.

Cold: Unprotected characters must make a Fortitude save each hour (DC 15, +1 per previous check) or take 5 points of cold subdual damage. Characters whose protection against cold is at least level 1 or higher (cold weather outfit, Cold Endurance feat) are safe at this temperature range. The range of this temperate is below the freezing point of water. Characters should bear in mind that magic potions and similar consumables and equipment may freeze at this temperature or lower.

Moderate: Moderate temperatures might be considered a mite nippy by some, but do not have an adverse affect of your character’s health. A brisk Autumn morning, or a cloudy Spring day might have moderate temperatures.

Warm: Warm temperatures usually reflect balmy summer days of peace and solitude. The upper extremes of this range may be a bit sticky and unpleasent for some, but the worse you could expect from going out in this weather is a bit of a headache.

Hot: In this temperature band, unprotected characters must make successful Fortitude saving throws each hour (DC 15, +1 for each previous check) or take 5 points of subdual fire damage. Characters wearing heavy clothing or any kind of armour take a -4 penalty on their saves. Characters whose protection against heat is at least level 1 (such as from the Heat Endurance feat or carrying a parasol) are safe at this temperature range and need not make the save.

Severe Heat: In this temperature band, unprotected characters must make a Fortitude save every 10 minutes (DC 15, +1 per previous check), or take 5 points of fire subdual damage on each failed save. A partially protected character need only check once per hour. Every time a character takes damage (but no more than once per round), the GM must make an attack roll agains the character’s Fortitude Defence to see if that character has contracted Heatstroke (q.v.). Characters wearing heavy clothing or any kind of armour take -4 penalties on their saves. For complete protection against severe heat, a character must have a level of protection of 2 or higher. A character whose level of protection is only 1 is considered partially protected.

Extreme Heat: Unprotected characters take 5 points of lethal fire damage, and 5 points of subdual fire damage, every ten minutes (100 rounds). The damage is inflicted in phase one of the one hundedth round.  Every time a character takes damage (but no more than once per round), the GM must make an attack roll agains the character’s Fortitude Defence to see if that character has contracted Heatstroke (q.v.). Those wearing metal armour or coming into contact with very hot metal are affected as if by a heat metal (q.v.) spell. A partially protected character takes damage once per hour instead of once per 10 minutes. A character must have a level of protection of 3 or higher to be protected against extreme cold. Level 2 is considered partial protection; level 1 is considered unprotected.

Unearthly Heat: In this temperature band, unprotected characters take 10 points of lethal fire damage, and 10 points of subdual fire damage, per minute (10 rounds). The damage is inflicted in phase one of the tenth round.  Every time a character takes damage (but no more than once per round), the GM must make an attack roll against the character’s Fortitude Defence to see if that character has contracted Heatstroke (q.v.). Those wearing metal armour or coming into contact with very hot metal are affected as if by a heat metal (q.v.) spell. Partially protected characters take damage once per 10 minutes instead of once per minute. For complete protection against the effects of unearthly cold, a character must have a level of protection of 4 or higher. Level 2 or 3 is considered partial protection, and level 1 is no protection at all.

Burning Heat: At some point, increasing temperatures push past even unearthly heat and graduate to actual burning – when material objects catch fire spontaneously due to the heat. For instance, paper catches fire at 451ºF (232ºC) – and dried-out skin catches fire at around the same temperature. Characters carrying fuel for their lamps or other combustibles discover that it catches fire at around 260ºF (127ºC). Water boils at approximately 212ºF (100ºC), depending on barometric pressure, and many potions or elixirs could quickly boil away to nothing somewhere near that temperature range.

In a region in this temperature band, characters take 15 points of fire damage per round. In addition, those wearing metal armour or coming into contact with very hot metal are affected as if by a heat metal (q.v.) spell (which lasts as long as the character remains in the area of burning heat). Generally, mundane methods of protection against heat offer no protection in areas of burning heat, and various levels of heat protection are meaningless if a creature is on fire unless it is immune or highly resistant to fire. Characters at this temperature automatically contract heatstroke on their first round of exposure.

Dehydration, Hypothermia and Heatstroke

Normally medium or small characters need to consume about one gallon of fluids (about 8 pints or 4½ litres) per day to stave off dehydration. For each temperature band hotter than Hot in the above table, your character needs to consume one extra gallon. If you don’t drink this your start to get dehydrated, and you may eventually die of thirst. In temperature bands where the hydration suit provides complete protection for heat dangers, it allows the wearer to survive on just one gallon per day. I’ll get into dehydration, as well as dying of thirst (and hunger) in later posts. In the meantime, I think that’s all you really need to know.

Hypothermia and Heatstroke are afflictions, that work in the same way as diseases. They will be fully detailed when the section on Wounds and Healing is published to the blog just before Christmas. However, as they are essential to the understanding of this post as well, I’ll give you a quick preview:

HEATSTROKE (Level 5 Disease)
Any prolonged exposure to intensely warm environments can befuddle the mind and cause you to fall unconscious.
Attack: +7 vs Fortitude
Onset: Instantaneous
Saving Throw: Fortitude DC 17
Frequency: 1/hour

Initial Effect: Your skin turns red and becomes hot and dry to the touch. Your lips swell. Dehydration makes you a little nauseous. Gain the sickened condition.

Further Effects: While not fatal in and of itself, Heatstroke can leave a character helpless and at the mercy of an unforgiving envirnonment. Further failed saving throws impose the following cumulative effects:
    First failed save: You faint. You fall to the ground and are prone and helpless. You remain unconscious for about ten minutes, or until revived by your companions. From now on every time you engage in extreme physical activity (fighting, running, climbing, jumping) you must make a DC 17 Fortitude save or faint.
    Second failed save: You are pemanently under the effect of the Confused condition.
    Third failed save: You fall unconscious. You will not wake up of you own volition.

Cure: Characters making an effort to drink lots of fluids and protect their head with a sensible hat gain a +2 circumstances bonus to their Fortitude Defence and saving throws to resist the effects of Heatstroke.
    If the character can reach the shade and drink lots of fluids then the effects of Heatstroke will fade. The character still has to make saving throws for 1d2 hours. After that, it takes one hour for the effects of Heatstroke to be reversed. Another charcter with the Heal skill can make a check at DC 17 to accelerate the cooling process. In this case no further saves are required, and the sufferer recovers in one hour.
    Alternatively, the effects can be removed by a Cure Disease spell (DC 17) or Heal (DC 17)

HYPOTHERMIA (Level 9 Disease)
Hypothermia comes about through the cooling of the body’s core temperature, and is usually caused by exposure to extremely cold environments for an extended period of time. Victims suffer numbness, shivering, amnesia and death.
Attack: +10 vs Fortitude
Onset: Instantaneous
Saving Throw: Fortitude DC 20
Frequency: 1/hour

Initial Effects: You start shivering uncontrollably, and have trouble performing complex tasks with your hands. Take a -2 penalty to Sleight of Hand checks and all attack rolls. Your vision is also affected imposing a -2 penalty to sight-based Perception checks.

Further Effects: If left untreated, hypothermia can be very deadly, very quickly. Further failed saving throws impose the following effects:
    First failed save: You become pale, and your extremities turn blue. The penalty to skill checks increases to -5. Your shivering is much more pronounced. Reduce you speed to 10 feet per round. You are mildly confused. Every time you roll Wisdom or Intelligence based skill, roll twice and take the lower result.
    Second failed save: Skin becomes blue and puffy, muscle coordination disappears. You fall to the ground and can no longer walk, although you can crawl. You are permanently under the effect of the Confused condition.
    Third failed save: You die.

Cure: The effects will reverse themselves if you can get into a Warm environment (16°C to 32°C). Details of different types of environment are found in the section on Adventuring. However, even if you find such a refuge, you body warms up slowly. You continue to suffer the effects of hypothermia for 1d4 hours after getting somewhere warm. It then takes another hour to return to normal.
    Another character with the Heal skill can make a DC 20 check to accelerate the warming process. If this check is successful, you stop suffering the effects of hypothermia in one hour and do not need to make any further saving throws.
    Alternatively, the effects can be removed by a Cure Disease spell (DC 20) or Heal (DC 20).

Next

It’s back to the Combat Section. Atypical Combat is the next post.

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4 thoughts on “HD&D: Temperature Extremes

  1. Neil under the “Freezing Cold” band you said only supernatural realms get this low … may I direct you towards Vostok, where the lowest verifiable temperate was in 1983 (-89C) and where the *average* drops below -63C for 3 months of the year. OK, so you wouldn’t sunbathe unless you were from Norway, but human life can and does survive there. I’d suggest a lower bracket than the “Freezing Cold” one your proposing … Ducking Chilly perhaps?

  2. Hmmm. I’ve just looked at a satellite photo of Vostok. It’s looks pretty damn supernatural to me. The ring road is in the shape of an Elder Sign for one thing.

    But yes, given the evidence I will probably have to tweak the bands somewhat. I won’t introduce any more categories, just increase the width of the bands, and start Freezing Cold at -100°C instead.

  3. Neil says:

    I am nearing the end now and I must say I’m impressed by the detail you have gone into, however, if you continue to do this I don’t think we will ever get to play it! I therefore suggest that we start play testing now since the major sections have been completed, combat, magic, skills, character gen, movement. If we start playtesting you can still add stuff as we go along and the playtesting crucible should prove a good environment in which to quickly discard, or not ideas.

    On to some comments. Why do objects have a reflex saving throw? If they can’t move how can they not be hit, unless very small in which case the modifier to hit should be enough?

    I agree with the others that updating of the website can wait; its a nice idea but do you really have the time? Besides how many people actually use it to the degree that its current form is a problem?

    Temperature bands. Freezing cold: “only supernatural environments ever get this cold” err no, the Arctic and Antarctica can get to -80 or even -90 centigrade! As for your severe heat, I have been out in 52 degree heat and yes it is very hot but fire damage! The hottest recorded air temperature on Earth was about 66 centigrade.

    How is 80 to 99 degrees unearthly? What about boiling pools near volcanoes? Heat stroke or scalding surely?

  4. You make a number of points here Neil. I’ve folded all the replies into this entry for simplicity sake.

    Yes you’re right. We should start playtesting sooner rather than later. However, we’re not quite there yet. These are the essentials that still need to be done:

    1) Wounds and Healing
    2) Weapons
    3) Spells
    4) Character Classes
    5) Monsters

    There’s also the section on Atypical Combat as well, but we can probably get by without rules for siege warfare at the moment. The rest are definitely required, although we don’t need to do all weapons, all spells, all classes or all monsters. So it’s all doable it’s a question of when it gets done. I certainly want to playtest in 2010, but it may be the summer at this rate.

    Objects obviously need a Reflex Defence to there is a target number to make your attack rolls against. A Reflex Saving throw implies that the object is proactively doing something to get out of the way of an attack. So no, they probably don’t need Reflex Saving Throws.

    I’ve reached the point where I need to collate and rationalise my Iourn notes. I think the website is the best place to do this, but I’m not a fan of the current format. So the answer to your question of who will benefit from changing the site, the answer is ME! I’m not dropping everything to update Iourn.com and I can’t see myself making any noticeable progress for many months, but it’s something I’m working toward.

    As I mentioned to Jack, the temperature bands come straight out of the third edition rules. I’m generally unwilling to change something I know nothing about unless lots of people jump up and down and tell me otherwise. I’ll happily alter the temperature bands to make the range a little saner.

    As for being out in 52 Celsius.

    Well, you’re only taking subdual damage – which equates to headache, light sunstroke and fatigue. And you only take that damage once every 10 minutes if you fail a saving throw. And that assumes someone with absolutely zero protection against the sun – akin to standing in the middle of the desert stark naked and basting yourself with olive oil.

    If you’re a good sun hat and protective clothing then you only have to make the check once per hour instead of once every ten minutes. If you’re wearing a hat and applying some other form of heat protection such as a hydration suit – or 21st century sunscreen (which I’m sure you were wearing) – then you have complete protection and don’t take any damage at all.

    So it may not be completely right, but it’s not *that far* from reality, is it?

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