DnD 5e - Environment
Playing a game that simulates a real world involves simulating the mechanics of a real world and all of the hazards and complications which that entails. This section covers rules for day-to-day, real-world environmental phenomena which your characters will encounter.
The first two subsections are "Falling" and "Suffocating", but don't let that scare you. Not everything in this section will kill you; I've chosen to reflect the order used in the Player's Handbook to make it easier to cross-reference the two sections, and Player's Handbook doesn't like the sections in alphabetical order for some reason.
Whether you fall into a pit trap, get shoved off a cliff, or are dropped from a great height by a roc, falling is an ever-present danger for adventurers. If a creature falls a distance greater than 10 ft., they take 1d6 damage per 10 ft. fallen, up to a maximum of 20d6 damage. If you take damage from falling, you fall prone.
This rule, like others, may require some suspension of disbelief. Massively tall creatures like giants and dragons still take damage at the same rate, even though a 10 ft. fall might be like falling a distance as high as your knee. Fortunately, these creatures typically have massive pools of hit points, so 1d6 damage is a trivial amount of damage for them.
If you're worried about falling, consider having someone in the party learn the feather fall spell. It's also fun to note that the maximum falling damage is only 120, so at high levels many characters can survive a fall of any height.
A creature can hold its breath for a number of minutes equal to 1 + its Constitution modifier (minimum of 30 seconds, regardless of how bad its Constitution modifier is.). After that time, the creature runs out of breath.
When a creature runs out of breath or is choking, it can survive for a number of rounds equal to its Constitution modifier (minimum of 1 round). At the start of its next turn, it drops to 0 hit points and is dying, and it can’t regain hit points or be stabilized until it can breathe again. For more on dying, see Death and Dying, later in this guide.
For example, a creature with a Constitution of 14 can hold its breath for 3 minutes. If it starts suffocating, it has 2 rounds to reach air before it drops to 0 hit points. By comparison, a creature with 8 Constitution can hold its breath for just 30 seconds. If it starts suffocating, it has only one round to reach air before it drops to 0 hit points.
Vision and Light
Adventurers spend a lot of time looking at stuff. But, just like the real world, looking at stuff can get difficult sometimes. Stuff gets in the way, stuff is far away, stuff is the dark. When it's hard to see stuff, it's called "Obscurement". Obscurement comes in three levels levels: unobscured, lightly obscured, and heavily obscured. Obscurement can apply to whole areas, or to specific creatures or objects.
An area, creature, or object is unobscured if you have clear line of sight to it, and it is clearly lit. For example: an actor on a lit stage is typically unobscured, as are the area of the stage and the props on the stage.
A target is lightly obscured if it is dimly lit (see Dim Light, below), patchy fog, light foliage, or similar obstructions which make it difficult to see but doesn't totally block vision. Creatures have disadvantage on Wisdom (Pereeption) cheeks that rely on sight while in a lightly obscured area or while trying to see a lightly obscured creature.
A target is heavily obscured if vision is blocked entirely, such as by darkness (see Darkness, below), opaque fog, dense foliage, or similar obstructions. A creature in a heavily obscured area effectively suffers from the Blinded condition (see Conditions, later in this guide), and suffers all of the associate penalties.
Light and Darkness
Light comes in three levels: bright light, dim light, and darkness. Each can be produced under a wide variety of circumstances. The rules don't include guidelines for how light reflects and how shadows work, so such matters are typically left up to your imagination.
Bright light allows most sighted creatures to see normally, and includes anything as dim as a nearby torch all the way up to direct sunlight. Objects and spells which produce bright light will specify that they do so, and how far that light stretches. For example: a torch casts bright light 20 ft., while the daylight spell casts bright like 60 ft.
Dim light is light sufficiently difficult that seeing is possible, but a human must typically strain their eyes to see. You will most commonly encounter dim light at dawn and dusk, on nights with bright moonlight, or at the boundaries of torches and other light sources. For example: a torch casts 20 ft. of bright light and dim light for another 20 ft. beyond that radius.
Dim light is sometimes referred to as "shadows", and when a spell or ability refers to shadows, they typically mean dim light. In game terms, "shadows" does not include shadows cast by objects, so the shade of a tree on a sunny day doesn't produce dim light.
Darkness is a light level where humans are totally unable to see, such as a moonless night, in an unlight dungeon, or the inside of a closed barrel.
While humans are unable to see in total darkness, creatures with Darkvision can still see. However, this vision is limited both in function and range. This text is taken from the Dwarf's Darkvision entry in the dwarf racial traits.
You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.
Most creatures with Darkvision can see to a range of 60 ft., but some creatures can see further (for example, Drow have 120 ft. Darkvision), and a handful of creatures have Darkvision with less than 60 ft. range.
Some effects, such as the darkness spell, create areas of magical darkness. These areas override the normal light conditions in the area, reducing even bright light of the sun to total darkness.
Creatures with Darkvision are unable to see in magical darkness, just as other creatures are unable to see in mundane darkness. However, some creatures with exceptional abilities can see in magical darkness. The most common examples are devils, though warlocks with the Devil's Sight invocation can also see in magical darkness.
Some creatures possess a variety of special senses which allow them to percieve the world in ways in which a human cannot. Some examples are listed below, and are fully explained on page 9 of the Monster Manual.
- Blindsight: Some creatures, especially those without eyes, can sightlessly percieve the world around them out to a fixed range. These creatures are unaffected by light and darkness, and can percieve invisible creatures. Some creatures which rely on blindsight use echolocation, so they lose the benefit of blind sight partially or entirely if they lose the ability to hear.
- Darkvision: Some creatures are able to see out to a certain range in mundane darkness.
- Tremorsense: Some creatures are able to percieve vibrations in the ground, allowing them to pinpoint the locations of nearby creatures within a certain range. Creatures with this ability are often subterranean and have a burrow speed.
- Truesight: Some creatures have the exceptional ability to see the world as it truly is. Within a certain range they can see through all lighting conditions (including magical darkness), see invisible creatures, see through illusions, see the true forms of shapeshifters, and see into the ethereal plane. This is an exceptionally powerful ability possessed only by a tiny handful of handful of creatures.
Food and Water
Creatures (with some exceptions) require food and water. A medium-sized humanoid like an adult human requires roughly one pound of food and one gallon of water every day. If a creature's food or water needs are not met, they suffer levels of Fatigue which can't be removed until they recieve sufficient food and water.
In my experience, most groups don't worry about food and water except under extreme circumstances. One day of rations costs 5 silver pieces, but foraging is usually easy, and you can typically rely upon magic options like the spells goodberry, create or destroy water, and create food and water, some of which are available as early as 1st level.
In some cases, the Dungeon Master might make food and water a plot point by placing the party in a desert or some other resource-scarce environment, but even then magic options usually work unless the DM goes to great lengths to remove them. Dungeons and Dragons isn't a survival game, and tracking food and water rarely contributes to a fun game, so most of the time groups choose to just ignore it in the same way that most groups ignore mundane tasks like bathing and doing laundry.
Interacting with Objects
Your character can interact with objects in the game world in any way that a real person could interact with the same object in the real world: you can lift things, move them, push them about, poke them with sticks, etc. When you do so, the Dungeon Master dictates the outcome of those actions.
Like in the real world, you can also break stuff. This is done by one of two methods: First, you can simply attack the object. Every object has an AC and hit points just like a creature, both of which are determined by the object's size and the material from which it is made. You can hit an object with weapons, spells, or your bare hands, striking it until it breaks. The DM might decide that some objects are resistant or immune to certain damage types, like glass being immune to acid or wood being vulnerable to fire.
Second, you can attempt a Strength check to break an object. This is the equivalent of tearing a sheet of paper, snapping a wooden branch, kicking down a door, smashing a pot on the ground, etc. to destroy the object with a single action. The DM sets the DC of this ability check based on the size of the object and the materials from which it is made.