Variant Rules (Spelljammer Supplement)

Ship Rules

This setting uses Unearthed Arcana #55 "Of Ships and the Sea" with a handful of exceptions:

• Due to Mythic Monsters, ships can be larger than Gargantuan.
• While a ship has one-tenth of its crew or less, it can not use its movement actions (should be included in each ship's page).
• While a ship is occupied by more creatures than its crew and passenger maximums combined, each creature can breath for a number of hours equal to 1 + its Constitution modifier, after which it must hold its breath or begin suffocating.

Gravity

Any creatures and objects larger than Gargantuan exert gravity on their surroundings in a radius equal to twice the creature or object's radius. Unless acted upon by an outside force, this gravity is always equal to Earth's gravitational force and is toward the center of the creature or object. While outside of a gravitational field, a creature can not use their walking, swimming, or flying speed. If a creature moves without using their climbing speed, such as by jumping or being shoved, they move the same amount in the same direction at the beginning of each of their turns until they move in a different direction. A DM might call for a Strength (Athletics check to move in a different direction if a creature is moving fast enough.

Divine Magic in Space

It is difficult for a cleric, druid, paladin, or warlock to communicate with their deity or force of nature outside of their crystal sphere of origin. 3rd-level or higher spells of these classes cannot be cast while outside of their crystal sphere of origin. 1st- and 2nd-level spells can still be cast using higher level spell slots.

While within a crystal sphere not of their origin, a creature might seek out a deity of the same domain, or potentially even an aspect of the same deity, allowing them to ignore this rule while within that sphere.

Interplanar Magic in the Phlogiston

While in the Phlogiston, travel between dimensions, such as through a plane shift spell, a conjure animals spell, or portable hole, is impossible unless aided by powerful magic like a wish spell.

Fire in Phlogiston

While outside of a crystal sphere, mundane fire is liable to ignite the phlogiston that permeates space. When a fire is lit while in the Phlogiston, every creature in a certain radius must make a DC 15 Dexterity saving throw, taking a certain amount of fire damage on a failure or half as much on a success, depending on the density of the surrounding phlogiston using the following table:

Density	Radius	Damage
Sparse	5 ft.	1d10
Average	10 ft.	2d10
Dense	20 ft.	4d10
Very Dense	40 ft.	8d10
Concentrated	60 ft.	16d10

Mythic Monsters

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