Radiation
In certain games, exposure to radiation might be a constant concern to characters, due to the vast number of sources that can produce it. All stars produce radiation in some variety, and planets closer to these stars typically suffer more severe effects than worlds farther away. Many futuristic technologies incorporate radioactive parts and fuel cells that can leak harmful radiation when ruptured or exposed. Ancient alien civilizations might leave behind powerful artifacts that emit harmful radiation. Whether the source of the radiation is natural or artificial, any character in an environment rich with radiation may suffer some negative effects for exposure.
Saving throws against radiation are treated as saving throws against poison for the purposes of features such as a Mutant's Robust Physiology feature.
Radiation Damage
Short bursts of radioactive energy cause radiation damage to creatures. Radiation damage is treated as poison damage, with the added effect of causing radiation exposure depending on the amount of damage taken.
Radiation Damage Exposure
| Damage | Degree of Exposure |
|---|---|
| 1 - 5 | Mild |
| 6 - 15 | Low |
| 16 - 30 | Moderate |
| 31 - 50 | High |
| 51+ | Severe |
Environmental Radiation
The presence of radiation sources may cause a location or object to constantly irradiate anyone within the location or in contact with the object.
Based on a creature's circumstances, consult the "Environmental Radiation Exposure" table to determine their degree of exposure based on total time of exposure within a given 24-hour period (rounding up). A character's exposure is determined either when the character is no longer exposed to radiation, or after a day has passed exposed to it, whichever happens first.
Radiation in Play
A lingering death from radiation sickness is dreadful, and it’s hardly heroic. The judicious use of radioactivity adds flavor and an element of danger to a modern game, but too much of it can impair an otherwise exciting campaign.
Radioactive items and areas are best used in the game when they force players to make difficult choices: Do we spend a week traveling around the irradiated ruins of a city, or, with time of the essence, do we risk crossing the dangerous area? Radioactive areas help define the geography in much the same way that oceans, mountains, and other impassable (or at least dangerous) terrain does. And they change the tactical landscape, especially when the heroes’ opponents are immune to the effects of (or simply don’t care about) radiation.
Radioactivity, and the threat of radiation sickness, adds a great bit of spice to play. Use it carefully, but don’t overdo it. Characters hampered by constant exhaustion as a result of radiation sickness can’t make the most of their adventures - and aren’t a lot of fun to play.
Irradiated Areas
Events such as nuclear bomb detonations, experiment accidents, and reactor breaches can cause a location to remain radioactive for an extended period of time. An irradiated environment has a degree of radioactivity, which affects all creatures within the location depending on how much time they spend there.
Radioactive Sources
Objects such as nuclear waste, alien artifacts, or items that have been exposed to radiation continuously often emit their own radiation. Creatures exposed to radioactive sources suffer exposure similarly to being in an irradiated area. Exactly what counts as exposure for different objects is determined by the GM, though it usually falls into the same categories as poisons - contact, ingested, inhaled or injury (Dungeon Master's Guide page 257).
Radiation Sickness
Characters exposed to radiation must make a Constitution saving throw or gain levels of exhaustion based on the severity of the exposure. After determining a creature's level of exposure, consult the "Radiation Sickness" table to determine the effects of their exposure.
Environmental Radiation Exposure
| Situation | 1 Round | 1 Minute | 10 Minutes | 1 Hour | 1 Day |
|---|---|---|---|---|---|
| Character in irradiated area | |||||
| Lightly Irradiated | mild | mild | mild | mild | low |
| Moderately Irradiated | mild | mild | low | low | moderate |
| Heavily Irradiated | low | low | moderate | moderate | high |
| Severely Irradiated | moderate | moderate | high | high | severe |
| Character exposed to radiation source | |||||
| Lightly Radioactive | mild | mild | low | low | low |
| Moderately Radioactive | low | low | moderate | moderate | moderate |
| Heavily Radioactive | moderate | moderate | high | high | high |
| Severely Radioactive | high | high | severe | severe | severe |
Radiation Sickness
| Degree of Exposure | CON Saving Throw DC | Success | Failure | Critical Failure |
|---|---|---|---|---|
| Mild | 5 | - | 1 level of exhaustion | 1 level of exhaustion |
| Low | 10 | - | 1 level of exhaustion | 2 levels of exhaustion |
| Moderate | 15 | - | 2 levels of exhaustion | 3 levels of exhaustion |
| High | 20 | 1 level of exhaustion | 3 levels of exhaustion | 4 levels of exhaustion |
| Severe | 25 | 2 levels of exhaustion | 4 levels of exhaustion | 5 levels of exhaustion |
For example, Steven is involved in a lab accident which causes the laboratory to become a moderately irradiated area. The evacuation process is fairly swift, and he manages to leave the area after 12 rounds after helping his his colleagues. Consulting the table, he is exposed to low radiation, and must make a DC 10 Constitution saving throw after leaving. Unfortunately, he critically fails and gains 2 levels of exhaustion, collapsing outside of the lab.
Long-Term Effects
If you want the effects of radiation to linger for longer and present a more permanent threat to increase the stakes, consider the following rule: whenever a creature gains 3 or more levels of exhaustion at once due to radiation, they gain a Lingering Injury (Dungeon Master's Guide page 272).
Treating Radiation Sickness
Radiation sickness can be treated by any effect that removes exhaustion, including resting. Additionally, certain advanced medicines can remove levels of exhaustion caused by radiation.
Radiation Spells
Like most aspects of the universe, radiation can be manipulated by magical forces. The following is a small selection of spells specially designed to harness the power of the atom.
Curie's Counterrad Field
4th-level abjuration
- Casting Time: 1 Action
- Range: Self (10-foot-radius sphere)
- Components: V, S, M (a pinch of powdered lead or lead filings)
- Duration: Concentration, up to 1 hour
A 10-foot invisible counterrad sphere surrounds you, blocking all radiation and suppressing any within the sphere. This area is unaffected by all forms of radiation, including those created by spells. Until the spell ends, the sphere moves with you, centered on you.
While an effect is suppressed, it doesn’t function, but the time it spends suppressed counts against its duration.
Creatures within the sphere are treated as if they are not exposed to radiation regardless of the circumstances, and are immune to radiation damage. Items powered by radioactive cells cease to function within the sphere.
Detect Radiation (Ritual)
1st-level divination
- Casting Time: 1 Action
- Range: Self
- Components: V, S
- Duration: Concentration, up to 10 minutes
For the duration, you sense the presence of radiation within 30 feet of you. If you sense radiation in this way, you can use your action to see a faint aura around any visible creature or object in the area that is radioactive, and you learn its level of radioactivity.
The spell can penetrate most barriers, but is blocked by 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt.
Oppenheimer's Scorched Earth
9th-level conjuration
- Casting Time: 1 Action
- Range: 1 mile
- Components: V, S
- Duration: Instantaneous
You create a small nuclear detonation at a point within range. Each creature in a 50-foot radius sphere centered on the point you choose must make a Constitution saving throw. The sphere spreads around corners. A creature takes 20d6 fire damage and 10d4 radiation damage on a failed save, or half as much damage on a successful one.
The spell damages objects in the area and ignites flammable objects that aren’t being worn or carried.
Rutherford's Withering Beam
2nd-level evocation
- Casting Time: 1 Action
- Range: 60 feet
- Components: V, S
- Duration: Instantaneous
A bright green beam of atomic energy streaks toward a creature in range. Make a ranged spell attack against the target. On a hit, the target takes 2d4 radiation damage.
At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the damage increases by 1d4 for each slot level above 2nd.
Suppress Source
1st-level abjuration
- Casting Time: 1 Action
- Range: 120 feet
- Components: V, S
- Duration: 10 minutes
Choose any radioactive creature or object within range. That creature or object is not considered a radiation source for the duration. If a creature under this effect attempts to use an ability or cast a spell that causes radiation damage, it fails.
At the end of each of it's turns, a creature affected by this spell can make a Constitution saving throw. On a success, the spell ends.
Credits
Document and contents by Dylan Richards (Reddit: u/Altavus , Tumblr: decision-paralysis, Blogger: Decision Paralysis)
Art
Source Material
"d20 Modern" role-playing game by Wizards of the Coast.
Built heavily upon "d20 Modern 5e Conversion" by Edward Wilson.