Plane

Definition
The planes of existence are different realities with interwoven connections. Except for rare linking points, each plane is essentially its own universe with its own natural laws.

Types

 * Material Planes are planes most familiar to most D&D characters, as they are the standard settings. They tend to be earth-like and operate under the same set of natural laws. Most campaigns have only one Material Plane as a setting, and it often provides the "home base" for that campaign.
 * Transitive Planes are planes that are grouped together due to their common use: getting from one place to another. The Astral Plane is used to reach other planes, while the Ethereal Plane and Plane of Shadow are both used for transportation within the Material Plane they are connected to. These planes have the strongest regular interaction with the Material Plane and often accessed by use of various spells.
 * Inner Planes are also called "planes of power," and are incarnations of the basic building blocks of the universe. They are made up of a single energy or element that overwhelms all others. These planes are often hostile to planar travelers, and should be crossed with extreme caution. These planes are divided into four groups: Energy Planes, Elemental Planes, Paraelemental Planes and Quasielemental Planes.
 * Outer Planes are the homes of beings of great power, and are also called the godly planes, spiritual planes or divine planes. The deities themselves live here, as do creatures such as celestials and fiends. The Outer Planes tend to have alignments, representing a particular moral or ethical outlook, and their inhabitants tend to behave in line with those outlooks. The Outer Planes are also the final resting place for spirits from the Material Planes, whether that final rest is calm introspection or eternal damnation.
 * Demiplanes is a catch-all category that covers all extradimensional spaces that function like planes, but have measurable size and limited access. Other kinds of planes are theoretically infinite in size, but a demiplane might only be a few hundred feet across. Access to demiplanes can be extremely limited. Some are created by spells, some naturally evolve, and others are created by deities.

Planar Traits
Each plane of existence has its own properties - the natural laws of its universe. All comparisons are made against the Material Plane, as it is the default setting, so other planes are similar to the default setting unless a plane's description says otherwise. Planar traits are broken down into a number of general areas. All planes have the following traits: While these traits are generally for the whole plane, certain locations may be exempt, whether due to natural, divine or arcane effects.
 * Physical Traits - These traits set the laws of nature, such as gravity or time.
 * Elemental or Energy Traits - These traits determine the dominance of particular elemental or energy forces.
 * Alignment Traits - Just as a character, a particular plane might be tied to a particular moral or ethical outlook.
 * Magic Traits - Magic works differently from plane to plane, and these traits set the boundaries for what it can and cannot do.
 * Other Traits - Other traits that may have effects on a plane or area not specified above.

Physical Traits
The physical traits of a plane set how gravity works, how time passes, the physical boundaries of a plane, the nature of those borders and the nature of matter itself.

Gravity
One variable that can change is the gravitational forces of the plane. It can be made heavier or lighter, and the direction of its pull may be from a different direction entirely.
 * Normal Gravity: Most planes have gravity similar to that of the Material Plane. That is, if something weighs 10 pounds there, it weighs 10 pounds here. The usual rules for ability scores, carrying capacity and encumbrance apply.
 * Heavy Gravity: The gravity of this plane is much more intense than that of the Material Plane. All physical skill checks and attack rolls suffer a -2 penalty if the individual is not a native. All item weights are doubled. Weapon ranges are halved. Fall damage is doubled.
 * Light Gravity: The gravity of this plane is less intense than that of the Material Plane. As a result, nonnatives can lift more, but their movements are ungainly. Nonnatives suffer a -2 penalty to most physical skill checks and attack rolls. All items weigh half as much. Weapon ranges double. Characters gain a +2 bonus to Climb and Jump checks. Fall damage is halved.
 * No Gravity: Individuals in a plane with no gravity merely float in space, unless other mechanisms (magic or force of will) are available to provide a direction for the gravity's pull, or provide momentum. An example of such is the Astral Plane, where everyone moves by simply willing themselves to move in a certain direction.
 * Objective Directional Gravity: The strength of the gravity is the same as the Material Plane, but the direction is not the traditional "down" toward the ground. It may be down toward any solid object, at an angle to the plane itself, or even upward, where everyone must hang on or be thrust into an endless void. In addition, the gravity's pull may change from place to place within the plane. Travelers on such planes tend to be very cautious, as a corridor can suddenly become a pit.
 * Subjective Directional Gravity: The strength of the gravity is the same, but each individual chooses the direction of the gravity's pull. Such a plane has no gravity for unattended objects and nonsentient creatures. This can be very disorienting to a newcomer, but is common on "weightless" planes such as the Plane of Air. Characters can move normally across a surface by imagining "down" near their feet. For pockets of matter in such a plane, this is teh most common way to generate one own's gravity. If suspended in mid-air, a character "flies" by choosing a "down" direction and "falling" that way. Under such a procedure,a character "falls" 150 feet in the first round and 300 feet in each succeeding round. Movement is straight-line only. .In order to "stop," one has to slow one's momentum by changing the direction (again, 150 feet in the new direction and 300 each round thereafter). It takes a Wisdom check (Medium DC) to set a new action as a free action. Any character who fails receives a +6 bonus until he or she succeeds.

Time
The rate of time's passage can vary among different planes, though it remains constant within one plane. Time becomes interesting when a traveler moves between planes, but it still moves at the same apparent rate for the traveler. In other words, time is always subjective for the viewer. If one is magically frozen for a year, when they awaken, while seconds have passed for him, a year has passed for everyone else. The same subjectivity applies to various planes. Travelers may discover they pick up or lose time as they travel, but from their point of view time always passes naturally. To the denizens of such a plane, time flows normally and they don't notice the shifts.
 * Normal Time: This is the standard rate of time passage. One hour here is equal to one hour on the Material Plane.
 * Flowing Time: On some planes, time can flow faster or slower. One may travel to another plane, spend a year there, and find only seconds have elapsed on the Material Plane. Everything on the Material Plane is only a few seconds older. But for the traveler and his items, spells and effects working on him, that year was entirely real. When designating how time works, put the Material Plane's time first. For the above example, one round = one year.
 * Erratic Time: Some planes have time that speeds up or slows down at random when a traveler enters or leaves such a plane. Use the below table:
 * Timeless: On these planes, time still passes, but the effects of time are diminished. Those effects should be specifically defined for such planes. Such conditions as hunger, thirst, aging, magic and natural healing may all be affected. If a plane is timeless in regards to magic, all "until end of turn" effects become "save ends" effects. If a plane is timeless in regards to natural healing, then extended rests are even less effective (50/50 chance of recovering even 1 Daily, only regain 1 healing surge a rest).

Shape and Size
Planes come in a variety of shapes and sizes. Most planes are infinite, or so large they may as well be infinite.
 * Infinite: These planes go on forever, though they may have finite components within them, such as spherical worlds. Or they may consist of ongoing expanses in two directions, like maps that stretch out infinitely.
 * Finite: Set borders and edges limit these planes. These edges may be borders with other planes or hard, finite borders such as the edge of the world or a great wall. Demiplanes are often finite.
 * Self-Contained: Here the borders wrap in on themselves, depositing travelers on the other sid eof the map. A spherical plane is an example of a self-contained and finite plane, but there can be cubes, toruses and flat planes with magical edges that teleport the traveler to the opposite edge when reached. Some demiplanes are self-contained.

Morphic Traits
These traits measure how easily the basic nature of the plane can be changed. Some planes are responsive to sentient thought, while others can only be manipulated by the extremely powerful. And some planes respond to physical and magical effects.
 * Alterable Morphic: These planes are the norm. Objects remains where they are (and what they are) unless affected by physical force or magic. You can build a castle, animate a statue, or grow crops in such a plane, changing your immediate environment as a result of tangible effort.
 * Static: These planes are unchanging. Visitors cannot effect living residents of the plane, nor objects those denizens possess. Any spells that would affect those on the plane have no effect. Even moving an unattended object requires a Strength check (Medium DC). Particularly heavy objects may be impossible to move.
 * Highly Morphic: On the opposite end of the spectrum are planes that are easily changed. Such planes react dramatically to specific spells, sentient thought or force of will. Others change for no reason at all. In the D&D Cosmology, the Outer Plane of Limbo is a highly-morphic plane.
 * Magically Morphic: Specific spells can alter the basic material of these planes. The Plane of Shadow, which can be drawn elsewhere and used to duplicate other spells, is a good example of a magically morphic plane.
 * Divinely Morphic: Specific, unique beings (deities or other similar great powers) have the ability to alter objects, creatures and the landscape on these planes. Ordinary characters find these planes similar to alterable planes in that they are affected by spells and physical effort. But deities can cause these planes to change instantly and dramatically, creating great realms for themselves. Most planes of the Outer Planes are divinely morphic, which is why deities choose to live there.
 * Sentient: These planes are ones that respond to a single thought - that of the plane itself. Travelers find the plane's landscape changing as a result of what the plane thought of the travelers, either becoming more or less hospitable depending on its reaction.

Elemental or Energy Traits
The Material Planes are made up of fundamental elements and energies. Which elements and energies those are may vary, but all the various universes have basic building blocks. Within the Multiverse, there are four basic elements and two types of energies that together make up everything. The Material Plane reflects a balancing of those elements and energies. The Inner Planes in particular are almost all dominated by one element or energy type. Other planes may show off various aspects of these elemental traits.
 * Air-Dominant: Mostly open space, these planes have just a few hints of floating stone or other elements. They usually have a breathable atmosphere, though there may be clouds of acidic or toxic gas on the plane. The gravity trait for such a plane is usually either objective directional, subjective directional, or no gravity. Creatures of the Earth subtype are extremely uncomfortable on such a plane.
 * Lightning-Dominant: These planes seem normal, but will have constant storms with frequent strikes of lightning and thunderous peals. Travelers here will take 2d8 lightning damage per round, and will be considered deafened (any resistance to thunder will ignore). Furthermore, those in metal armor will take an additional 2d8 lightning damage per round, due to their attractiveness to the lightning. Lastly, the constant distractions of lightning bolts and thunder gives a -2 to Will, which cannot be offset by resistances/immunities to lightning/thunder.
 * Earth-Dominant: These planes are mostly solid. Travelers who arrive here run the risk of suffocation if they don't reach a cavern or other pocket within the earth. Worse yet, individuals who cannot burrow are entombed in the earth and must dig their way out (one square of movement per round). Such planes generally have objective directional or subjective directional gravity. Creatures of the Air subtype are uncomfortable here, as these planes are tight and claustrophobic to them.
 * Fire-Dominant: These planes are composed of flames that continually burn without consuming their fuel source. Fire-dominant planes are extremely hostile to Material Plane creatures, and those without resistance or immunity to fire are soon immolated. Unprotected flammables catch fire almost immediately, and those wearing unprotected flammable clothing catch on fire. In addition, individuals take 3d10 points of fire damage every round they are in such a plane. In general, gravity here is normal. Creatures of the Water subtype are extremely uncomfortable here. Those made of water or ice take double damage each round.
 * Water-Dominant: These mostly liquid planes likely drown those who cannot breathe underwater or reach a pocket of air. The gravity trait for such a plane is usually either objective directional, subjective directional, or no gravity. Creatures of the Fire subtype are extremely uncomfortable in such planes, and those made of fire take 1d10 points of damage each round.
 * Cold-Dominant: These planes are incredibly cold, falling well-below any temperatures known to the Material Planes. Any liquid will freeze in such an environment unless protected by magical means, and fires are nearly impossible to maintain. Individuals take 2d10 points of cold damage every round.
 * Acid-Dominant: These planes are ones in which the acid hangs thick in the air, corroding all it touches. Unprotected items are destroyed by the corrosive nature of such places, and individuals take 1d10 acid damage per round, as well as suffering a -2 to AC as even magical armor isn't quite as effective in such places (immunity or resistance to acid will not protect from this effect).
 * Poison-Dominant: These planes are often homes to creatures well-versed in the poisonous arts, and such places are rife with poison in the air, harming those who breathe it in. Individuals take 2d12 poison damage per round, as well as suffering a -2 to Fortitude as thy are weakened by the constant poisoning (immunity or resistance to poison will not protect from this effect).
 * Positive-Dominant: An abundance of life characterizes these planes. The two kinds are minor positive dominant and major positive dominant. A minor positive dominant plane is a riotous explosion of life in all its forms. Colors are brighter, flames hotter and sensations more intense. All individuals in such a place gain Regeneration 5. Major positive dominant planes go even further. Creatures on such a plane must pass a saving throw or be blinded for ten rounds. Simply being on such a plane grants Regeneration 10. Furthermore, those at full hitpoints gain 5 temporary hitpoints every round, which are cumulative. However, if the individual's temporary hitpoints exceed their normal hitpoints, they explode in a riot of energy and die. The positive energy protection spell prevents its target from receiving the regeneration, blindness or temporary hitpoints from this trait.
 * Negative-Dominant: These planes are vast, empty reaches that suck the life out of travelers who cross them. They tend to be lonely, haunted planes, drained of color and filled with winds bearing the soft moans of those who died winthin them. On minor negative dominant planes, living creatures take 2d6 necrotic damage per round. At 0 or less hit points, they crumble into ash. On major negative dominant planes, the damage is far greater, with living creatures taking 4d6 necrotic damage. At 0 or less hitpoints, they become a wraith. The negative energy protection spell prevents a traveler from taking this damage.

Alignment Traits
Certain planes, in particular those of the Outer Planes, have alignments. Most of the inhabitants will share that alignment, even deities. In addition, those who do not share that alignment often have difficulty on the plane. How a plane develops an alignment is a bit of a "chicken or the egg" scenario. Certain planes are predisposed to certain alignments, so creatures of those alignment tend to settle there. This makes the plane even more disposed to that alignment, and so on. Alignment traits have three components. One is the moral (good or evil), another is the ethical (lawful or chaotic) and the third is the strength of this disposition.
 * Good-Aligned/Evil-Aligned: These planes have chosen a side of the moral dilemma. Think celestials versus fiends.
 * Law-Aligned/Chaos-Aligned: These planes have chosen a side of the ethical dilemma. Think demons versus devils, which is the basis for the eternal Blood War.
 * Mildly-Aligned: Creatures who have an alignment opposite a mild alignment of a plane suffer a -1 to all d20 rolls, including attack rolls, saving throws, initiative and skill checks.
 * Strongly-Aligned: Creatures who do not share the the strong alignment suffer a -1 to all attack rolls, saving throws, initiative and skill checks.
 * Neutral-Aligned: Most planes not of the Outer Planes are mildly Neutral-aligned, meaning no creature suffers any penalties (as there is no opposite to Neutral). In a strongly Neutral-aligned plane, all creatures who are not both morally and ethically Neutral will suffer the above penalties (and such penalties stack, so a chaotic evil or lawful good character suffers a -2 to all d20 rolls).

Magic Traits
The magic trait tells how a plane handles spells and supernatural abilities. As with other traits, the magic trait describes how magic works compared to how it works on the Material Plane. Particular locations on a plane may have different magic traits.
 * Normal Magic: This magic trait means everything functions as written.
 * Dead Magic: These planes have no magic at all. Such a plane functions as if an antimagic field spell were in effect. Arcane powers do not function here at all. Divination spells and rituals cannot detect a subject within such a plane, nor can a spellcaster or ritual caster use spells or rituals to move in and out. Permanent planar portals still function. Spellcasters on such a plane feel uncomfortable and experience mild headaches.
 * Wild Magic: Spell and spell-like abilities (so anything using an implement) function in wildly different and sometimes dangerous ways on planes with the wild magic trait. Any spell or spell-like ability has a chance to go wry. The caster must make a skill check in accordance with the type of power used (Divine - Religion, Arcane - Arcana, etc), DC is 15+level of the power. In addition, certain such planes may give modifiers to certain types of spells or casters. Failure means something strange happens (see below table).
 * Impeded Magic: Casting particular spells or using particular abilities requires passing a skill check of the appropriate type at a DC of 15 plus the level of the spell or power in question. "Appropriate" DCs are determined by the power type of the spell or power. Failure still means the power and action are expended.
 * Arcane and Shadow spells or powers use Arcana
 * Divine spells or powers use Religion
 * Primal spells or powers use Nature
 * Martial spells of powers use Athletics or Acrobatics (user's choice)
 * Enhanced Magic: Particular spells and spell-like abilities are more powerful. This has several different definitions (see below). Also, enhanced spells treat immunity as "Resist 30."
 * Maximized: the spell or power deals maximum damage
 * Enlarged: bursts and blasts increase their size by 1
 * Empowered: damage is increased by half again (does not include extra damage, critical damage dice [if applicable] and extra damage dealt due to vulnerabilities).
 * Extended: until end of next turn effects become save ends, and "sustain" effects are now until the end of the encounter.
 * Limited Magic: These planes only permit spells and spell-like abilities from certain schools to be cast. Other spells or spell-like abilities treat the plane as a dead magic plane.

Other Traits
These are traits that do not fit into the above categories, but affect planes and regions nonetheless.
 * Entrapping: The plane or region is pulls travelers to stay, willing visitors to remain permanently. Once per week, the plane "attacks" a visitor, Level + 3 versus Will. On success, the target cannot leave the plane willingly.
 * Diseased: The plane or region is rife with disease, either from the air, vermin, pests or magic. Every day, visitors are "attacked" by the plane or region in question, Level + 5 versus Fortitude. On success, the target is afflicted with a Level +/- 1 disease of DM's choice.
 * Will-Sapping: The plane or region drains the Will of those traveling within it. Every day, visitors are "attacked" by the plane or region in question, Level + 3 versus Will. On success, the target loses -1 Will (maximum loss is -3 Will), and this effect cannot be removed until the one afflicted leaves the plane or region for a week.
 * Dark: Light sources don't work and the plane or region is pitch black.