The Planes

The Outer Planes are realms of spirituality and thought. They are the spheres where celestials, fiends, and deities exist.   The Inner Planes exemplify the physical essence and elemental nature of air, earth, fire, and water.   Planar Categories:

• The Material Plane and Its Echoes: The Feywild and the Shadowfell are reflections of the Material Plane.
• The Transitive Planes: The Ethereal Plane and the Astral Plane are mostly featureless planes that serve primarily as pathways to travel from one plane to another.
• The Inner Planes: The four Elemental Planes (Air, Earth, Fire, and Water), plus the Elemental Chaos that surrounds them, are the Inner Planes.
• The Outer Planes: Everything else. The Underworld and it's subcategories (Tír na nÓg and The Nine Hells)

• When adventurers travel to other planes of existence, they undertake a legendary journey that might force them to face supernatural guardians and undergo various ordeals. The nature of that journey and the trials along the way depend in part on the means of travel, and whether the adventurers find a magic portal or use a spell to carry them.

• “Portal” is a general term for a stationary interplanar connection that links a specific location on one plane to a specific location on another. Some portals function like doorways, appearing as a clear window or a fog-shrouded passage, and interplanar travel is as simple as stepping through the doorway. Other portals are locations — circles of standing stones, soaring towers, sailing ships, or even whole towns — that exist in multiple planes at once or flicker from one plane to another. Some are vortices, joining an Elemental Plane with a very similar location on the Material Plane, such as the heart of a volcano (leading to the Plane of Fire) or the depths of the ocean (to the Plane of Water).
• Passing through a planar portal can be the simplest way to travel from the Material Plane to a desired location on another plane. Most of the time, though, a portal presents an adventure in itself.
• First, the adventurers must find a portal that leads where they want to go. Most portals exist in distant locations, and a portal’s location often has thematic similarities to the plane it leads to. For example, a portal to the heavenly mountain of Celestia might be located on a mountain peak.
• Second, portals often have guardians charged with ensuring that undesirable people don’t pass through. Depending on the portal’s destination, “undesirable people” might include evil characters, good characters, cowards, thieves, anyone wearing a robe, or any mortal creature. A portal’s guardian is typically a powerful magical creature, such as a genie, sphinx, titan, or native of the portal’s destination plane.
• Finally, most portals don’t stand open all the time, but open only in particular situations or when a certain requirement is met. A portal can have any conceivable requirement, but the following are the most common:
• Time: The portal functions only at particular times: during a full moon on the Material Plane, or every ten days, or when the stars are in a particular position. Once it opens, such a portal remains open for a limited time, such as for three days following the full moon, or for an hour, or for 1d4 + 1 rounds.
• Situation: The portal functions only if a particular condition is met. A situation-keyed portal opens on a clear night, or when it rains, or when a certain spell is cast in its vicinity.
• Random: A random portal functions for a random period, then shuts down for a similarly random duration. Typically, such a portal allows 1d6 + 6 travelers to pass through, then shuts down for 1d6 days.
• Command Word: The portal functions only if a particular command word is spoken. Sometimes the word must be spoken as a character passes through the portal (which is otherwise a mundane doorway, window, or similar opening). Other portals open when the command word is spoken and remain open for a short time.
• Key: The portal functions if the traveler is holding a particular object; the item acts much like a key to a door. This key item can be a common object or a particular key created for that portal. The city of Sigil above the Outlands is known as the City of Doors because it features an overwhelming number of such item-keyed portals.
• Learning and meeting a portal’s requirements can draw characters into further adventures as they chase down a key item, scour old libraries for command words, or consult sages to find the right time to visit the portal.

• A number of spells allow direct or indirect access to other planes of existence. Plane shift and Gate can directly transport adventurers to any other plane, with different degrees of precision. Etherealness allows adventurers to enter the Ethereal Plane. And the Astral Projection spell lets adventurers project themselves into the Astral Plane and from there travel to the Outer Planes.