Clarifications on Light and Darkness

( ⇪ House Rules )

If the specifics about lighting conditions don’t matter to you, you can skip this section.

Using Light Sources

If an object or creature is partially revealed by light, it’s lit only on that side.

If a bright light you control passes over something because you moved, your passive spot check applies as normal (it isn’t concealed). Otherwise the GM secretly rolls doubly-effective concealment for it (celestial/atmospheric concealment apply as normal).

When handling a light source that has a specific direction, you must have the light source in-hand to use it effectively, and if it’s in-hand you can change its direction by up to 180° as a free action on your turn once per round (this is not a swift action).

If you change the direction of a light source such that the lighting conditions on something are the same both before and after changing direction but not in-between, you get a brief glimpse of everything that you would see if you were to stop your light in that direction, but your GM determines secretly whether you actually notice it. First, he rolls doubly-effective concealment as shown below (celestial/atmospheric concealment apply as normal).

  • Both bright light and shadowy illumination passed over it: 20% (doubled from 10%)
  • Only bright light passed over it: 30% (doubled from 15%)
  • Only shadowy illumination passed over it: 60% (doubled from 30%)

If you succeed, the GM then determines whether you would passively spot it (as if it were in bright light).

Seeing Distant Light

(Underdark page 106 sidebar)

Complete Darkness: In general, a light source can be spotted (Spot DC 20) at a distance equal to 20 times its radius of illumination, if the area is otherwise in complete darkness. For example, a sunrod can be seen from 600 feet away, provided that nothing obstructs the line of sight. An observer who fails this Spot check automatically spots the light source at half that distance.

Dim Light: In conditions equal to starlight or moonlight, a light source can be spotted (Spot DC 20) at a distance equal to 10 times its radius of illumination. For instance, a sunrod can be seen from 300 feet away in these conditions. An observer who fails this Spot check automatically spots the light source at half that distance.

Using Distant Illumination: Creatures outside the illumination of a light source can see into it just fine. An observer who is close enough to spot the light source automatically (10 times the radius of illumination in complete darkness, or half that in dim light) can make Spot checks as normal to discern creatures or objects in the illuminated area.

Light and Darkness Descriptor Effects

Effects with the [light] and [darkness] descriptors mutually counter and dispel effects of the other type of an equal or lower level. The terms “shadowy light” and “dim light” refer to the same lighting condition.

The key to understanding how magical darkness affects non-magical light is to understand that in each case of a darkness effect it says something about how it affects non-magical light. It’s not just talking about local light sources within the area, but ALL non-magical light sources that might be penetrating the area, including sunlight and moonlight. Once that’s understood, the rest makes a lot more sense.

Table: Example Light And Darkness Effects
Level Descriptor Spell Name Spell Summary
0 [Light] Light Emanates magical bright light to 20 ft then emanates magical shadowy light another 20 ft.
0 (none) No light Spreads non-magical pure darkness to 20 ft and non-magical lights can’t light the area, but it has no effect on darkvision throughout.
1 [Light] Light of lunia Emanates magical bright light to 30 ft then emanates magical shadowy light another 30 ft, and later allows the caster to shoot eye beams.
1 [Darkness] Darklight Only useful in non-magical pure darkness. Emanates special “darklight” to 5 ft, causing people inside the sphere to see normally despite the darkness, but has no effect on darkvision throughout.
2 [Light] Continual flame Emanates magical bright light to 20 ft, then emanates magical shadowy light another 20 ft
2 [Darkness] Darkness Emanates magical shadowy light to 20 ft, and non-magical lights can’t light the area, effectively making the area have non-magical pure darkness, but darkvision is partially affected by the shadowy light anyway.
3 [Light] Daylight Emanates magical bright light to 60 ft then emanates magical shadowy light another 60 ft.
3 [Darkness] Blacklight Emanates magical pure darkness to 20 ft, impenetrable to everyone except to the caster inside the area, and even blocks darkvision.
3 [Darkness] Deeper darkness As the Darkness spell, but emanates to 60 ft.

Any time a spell of one descriptor is cast to overlap or moves into the area of a spell of the other descriptor, a special zone exists as the overlapped area of the magical shadowy illumination (or bright light) and magical darkness. For these purposes, do not account for low-light vision when determining the radius of magical light. If both spells are the same level, the overlapped zone is lit (or lacks light) as if neither spell was in effect there (this is what is meant by the “otherwise prevailing conditions” of the area). If they are not of the same level, the zone is instead affected by the higher-level spell. Keep in mind that if no prevailing light sources (such as sunlight) have sufficient range or line of effect to the zone, the zone has non-magical darkness regardless.

If you anticipate having zones of prevailing conditions, non-magical light (e.g. sunlight, moonlight, a torch, etc.) allows you to see into those zones. For example, assume a scenario in natural broad daylight, where an area of a darkness spell partially overlaps an area of a continual flame spell. The two spells have equal spell levels, so the overlapped zone has the prevailing conditions of natural broad daylight (since natural broad daylight can pass through the area of the continual flame spell).

Celestial and Atmospheric Concealment

Usually only the GM cares about this, so you can skip this subsection.

Table: Concealment by Time of Day
Dawn Hours Dusk Hours Concealment
9 AM onward before 6 PM 0% (broad daylight)
8~8:59 AM 6~6:59 PM 5%
7~7:59 AM 7~7:59 PM 10%
6~6:59 AM 8~8:59 PM 15%
before 6 AM 9 PM onward 20% (assuming clear moonlight and clear starlight, see below)

Having a working light source (such as a lit torch) eliminates all celestial/atmospheric concealment within its brightly-lit area and celestial/atmospheric concealment is only 2/5 (40%) as effective (the ratio between concealment and total concealment) in areas of shadowy illumination from such a light source. For example, a lit torch at 7:30 PM (10% daytime concealment) eliminates all of the 10% concealment provided by dusk within its zone of bright light and there’s only 4% concealment in the torch’s zone of dim illumination.

The following celestial/atmospheric conditions each add 10% to the 20% value for nighttime lighting conditions up to a limit of 50% (total concealment) when relevant.

  • Less-than-half moonlight (half-moon or less)
  • No moonlight (no moon or new moon, stacks with less-than-half moonlight)
  • Significant cloud cover (reducing starlight)
  • Overcast cloud cover (eliminating starlight; stacks with “significant cloud cover”)

Of notable exception to the list above is a downpour, which explicitly conceals as fog (20% concealment beyond 5 feet) but should stack with the above table and list.

Celestial/atmospheric concealment stacks with all other forms of concealment (such as undergrowth) up to a limit of 50%. As soon as the total degree of the varying kinds of concealment reaches 20%, it counts as “concealment” for the purposes of effects affected by concealment (such as the ability to do a sneak attack), and as soon as it reaches the limit of 50% it counts as “total concealment” (as if pitch black).

A character with low-light vision is unhampered by celestial and atmospheric concealment until that concealment surpasses 20%, and even then they only are affected by concealment as much as that value surpasses 20%. For example, a character with low-light vision can see just as well at night as within daylight unless one of the items in the list above (such as less-than-half moonlight) is in play, and even then they’re only affected as much as those items surpass the normal 20% (so for less-than-half moonlight alone, 10% concealment is applied). As mentioned above, this only starts counting as “concealment” for effects affected by concealment once it reaches 20% and counts as “total concealment” once it reaches the limit of 50%.

When celestial/atmospheric concealment is in play, reduce the distance at which spot checks can be made in the environment (except for dungeons, which celestial/atmospheric concealment is irrelevant) by a percentage of the normal distance equal to double the amount of celestial/atmospheric concealment in play (apply the percentage reduction after the roll to determine normal spot distance is made, rounding the reduction down to the farther 5 feet). Thus, in 50% celestial/atmospheric concealment (i.e. total concealment) the character is effectively blind and as such has a 100% chance of failing the spot check unless they have some other kind of light source.

When celestial/atmospheric concealment is in play and a spot check is called for, first roll doubly-effective concealment provided by mundane darkness and celestial/atmospheric conditions. Thus, at 50% (i.e. total concealment) the character is effectively blind and as such has a 100% chance of failing the spot check unless they have some other kind of light source.

Clarifications on Light and Darkness

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