Gravity Variations (5e Variant Rule)

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The Basic Mechanics[edit]

Most Dungeons & Dragons campaigns take place on a singular planet, with additional planes of existence to go with it. Additionally, these planes of existence all have the same gravity as Earth, or whatever variant of Earth is being used, of 1 g, or 9.81 m/s^2. For this reason, there are no official mechanics for dealing with worlds with different levels of gravity. This is fine for most dungeon masters, but for those who wish to run an interplanetary D&D campaign, or something of the sort, this set of rules should help with that.

Gravity Tolerance[edit]

With this rule, each creature has a base optimal gravity, which is determined by the planet or moon that they grew up on or have recently spent a lot of time on. They also have a range of gravity tolerance. The upper limit of a creature’s gravity tolerance range is either a) the creature’s optimal gravity + 0.5 m/s^2 or b) the creature’s strength score in m/s^2, whichever is higher. For the purpose of calculating this, the creature’s strength score is considered to be doubled for each size category below medium, and halved for each size category above medium, as well as doubled if the creature has the powerful build feature, innate magical abilities, ki, or Charisma as their spellcasting ability (if the creature has multiple such features, they do not stack, except with changes in size category; the effective strength score is only doubled once after being changed by size category). The lower limit in m/s^2 is the creature’s optimal gravity – 1 – the creature’s Dexterity modifier, to a minimum of 0.5 m/s^2. Any creature in a location outside of its gravity tolerance range suffers certain penalties as described later.

A creature can adapt to shift its gravity tolerance range. Whenever a creature is on a planet or moon (or even plane of existence) with gravity other than their optimal gravity, the creature’s optimal gravity will gradually shift towards that level of gravity. The creature’s optimal gravity will increase or decrease at a rate of 1 m/s^2 per increment, where an increment is equal to 60 days divided by the creature’s Constitution modifier (minimum modifier of 1). A creature can also train to increase the upper limit of its gravity tolerance range. If the local gravity is within a creature’s gravity tolerance range, it can spend 3 hours a day exercising its body, increasing only the upper limit of its range without changing anything else (at the same rate specified above). This change lasts for a number of years after the creature stops training equal to its Constitution modifier (minimum 1).

Training or adaptation aside, the upper limit of a creature’s gravity tolerance range cannot exceed twice the limit determined by the creature’s Strength score, except by magical or evolutionary means.

Varying Gravity: Basic Effects[edit]

There are many benefits that result from low gravity, such as jumping higher and further, being able to carry larger loads, and projectiles flying further. These benefits are also reversed by high gravity. The following mechanical effects occur in low gravity, regardless of optimal gravity range:

  • The weight of an object or creature is equal to its standard weight as shown in the PHB (or wherever the item is written) × the local gravity in m/s^2 ÷ 9.81.
  • The normal range of a weapon increases by a number of feet equal to 10 × (9.81 – the local gravity in m/s^2), rounded to the nearest 5 feet. The long range is equal to the standard long range × 9.81 ÷ the local gravity in m/s^2.
  • A creature’s jump distance and height are equal to its standard jump distance and height × 9.81 ÷ the local gravity in m/s^2.
  • If the local gravity is under 7 m/s^2, heavy weapons no longer have the heavy property and normal weapons become light. If the local gravity is under 4 m/s^2, this is taken a step further, with even heavy weapons becoming light. Special weapons can be made that are only wieldable in low gravity, and are considered heavy x2, heavy x3, etc. If the local gravity is 13 m/s^2 or higher, light weapons lose the light property, normal weapons become heavy, and heavy weapons become unwieldable. If the local gravity is 16 m/s^2 or higher, this is taken a step higher (you get the idea–basically every increment of 3 m/s^2). Special weapons can be made that retain the light property even in high gravity, and are considered light x2, light x3, etc.
  • Terminal velocity equals standard terminal velocity in m/s × the local gravity in m/s^2 ÷ 9.81 m/s^2.

Low Gravity Drawback: Maneuvering[edit]

Moving in the way that one does on Earth, maneuvering on a low-gravity planet would be nearly impossible. That is why one must be extremely agile and quick to react in order to prevent oneself from tumbling out of control. If the local gravity is below a creature’s gravity tolerance range and the creature is not flying, it suffers the following effects:

  • If the creature has not moved on its previous turn, it can only reliably move up to half its speed on its current turn and cannot dash, except by magical means. If it attempts otherwise, it must succeed on a Dexterity (Acrobatics) check or fall prone and skid 10 feet in the direction it was moving. The DC of this check equals 10 + the creature’s optimal gravity in m/s^2 – the local gravity in m/s^2, rounded down, and increases by 5 if the creature attempts to dash or has already dashed this turn. This effect is nullified if the creature has a climbing speed and opts to use that instead of its normal speed.
  • Standing up from prone reduces the creature’s remaining movement to 0, rather than simply taking half its movement. This effect is nullified if the creature has a climbing speed and opts to use that instead of its normal speed.
  • All attacks made by the creature have disadvantage. This effect is nullified if the creature is wearing armor that has a prerequisite Strength score.

High Gravity Drawback: Standing and Moving[edit]

High Gravity Drawback: Standing and Moving The main drawback of high gravity is pretty obvious: you and everything you are carrying are way heavier. A creature cannot function properly in high-gravity environments except with great Strength or training (see above), and will even die after a few hours or days as the blood in their veins fails to give their brain enough oxygen (or a similar adverse effect if the creature doesn’t have blood). If the local gravity is above a creature’s gravity tolerance range and it is not flying by magical means, it suffers the following effects:

  • The creature’s speed is halved.
  • Any attempt to dash requires the creature to succeed a Strength (Athletics) check with a DC equal to the local gravity in m/s^2, rounded up.
  • If the creature’s exhaustion level is 0, it suffers one level of exhaustion after a number of hours equal to its Constitution modifier (minimum 1). This time is doubled if the creature has ki or can cast spells using Wisdom or Charisma. The creature’s exhaustion level cannot be reduced below 1 except by magical means. This effect persists even if the creature is flying by magical means as mentioned above.
  • Melee and thrown weapon attacks made by the creature have disadvantage.
  • Standing up from prone takes the creature’s full movement and an action, rather than just half the creature’s movement.

As the local gravity becomes stronger, a creature will suffer even further. If the local gravity exceeds 1.5 × the upper limit of the creature’s gravity tolerance range, the creature is considered to be suffering from very high gravity, and suffers the following effects:

  • The creature’s speed is reduced to 0, unless it succeeds on a Strength (Athletics) check with a DC equal to the local gravity in m/s^2, rounded up, in which case it can move up to 5 feet on its turn, or 10 feet on a critical success. Dashing is impossible except by magical means, and even then, the creature must repeat the check in order to do so.
  • The creature’s exhaustion level continues to increase at the same rate as stated above, and cannot be reduced at all except by magical means.
  • The creature cannot wield weapons that don’t have the light property. Any weapon attack the creature makes has disadvantage.
  • A prone creature attempting to stand must succeed on Strength (Athletics) check with a DC equal to half the local gravity in m/s^2 in order to do so. A standing creature must repeat the check with advantage, falling prone again and taking 1d4 points of bludgeoning damage on a failure.

Additional Spells[edit]

With this new supplemental set of rules comes the opportunity for new spells. The following spells appear on the druid, sorcerer and wizard spell lists, except for the gravity resistance cantrip, which appears on the spell list of every class that has cantrips.

Gravity Resistance[edit]

Abjuration cantrip

Casting Time: 1 bonus action

Range: Touch

Components: S

Duration: 1 minute

You touch a creature, and the upper limit of its gravity tolerance range temporarily increases for the duration, by an amount in m/s^2 equal to your spellcasting ability modifier.

Gravity Well[edit]

1st-level transmutation

Casting Time: 1 action

Range: 120 feet

Components: V, S

Duration: Concentration, up to 1 minute

You gesture toward a creature you can see within range, and it must make a Charisma saving throw. The creature automatically succeeds the save if it is being magically protected from the effects of high gravity. On a failed save, the creature experiences the effects of gravity just above its gravity tolerance range until your concentration ends. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, you may target one additional creature for each slot level above 1st.

Gravitational Bind[edit]

3rd-level transmutation

Casting Time: 1 action

Range: 60 feet

Components: V, S

Duration: Concentration, up to 1 minute

Up to two creatures you can see within range must each make a Charisma saving throw. A creature automatically succeeds the save if it is being magically protected from the effects of high gravity. On a failed save, the creature experiences the effects of gravity in m/s^2 equal to twice your spell save DC until your concentration ends. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, you may target one additional creature for each slot level above 3rd.

Adjust Gravity[edit]

4th-level transmutation

Casting Time: 1 action

Range: 100 feet

Components: V, S, M (some kind of balancing tool, such as a scale or a gyroscope)

Duration: Concentration, up to 1 minute

This spell changes the local gravity in a 50-foot-radius, 100-foot-high cylinder centered on a point within range. When you cast this spell, the local gravity within the cylinder increases or decreases by up to 5 m/s^2 and remains that way until your concentration ends, but cannot decrease below 0.

At Higher Levels.' When you cast this spell using a spell slot of 5th level or higher, the amount by which you may adjust the gravity increases by 1 m/s^2 for each slot level beyond 4th.

Gravity Immunity[edit]

6th-level abjuration

Casting Time: 1 minute

Range: 60 feet

Components: V, S, M (a small scale)

Duration:' 24 hours

When you cast this spell, you and up to 10 creatures you can see within range become immune to the negative effects of gravity for the duration. Until the spell ends, the optimal gravity of an affected creature automatically adjusts to remain equal to the local gravity. When the spell ends, the creature’s gravity tolerance goes back to what it was before you cast the spell.

Power Word Crush[edit]

9th-level evocation

Casting Time: 1 action

Range: 60 feet

Components: V

Duration: Instantaneous

You speak a word of power that causes a creature you can see within range to briefly experience crushing gravity. If the upper limit of the creature’s gravity tolerance range in m/s^2 is less than your spell save DC, the creature instantly falls prone and takes 100 points of bludgeoning damage.



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