Portals

Definition
A portal is a general term for any stationary interplanar connection. Portals, which include related items such as vortices or gates, open at one location on the originating plane and at one location on the destination plane (or planes).

A portal may be transparent, translucent or opaque. A transparent portal looks like a doorway or window looking into another plane. Some allow a view to the destination, others do not.

Planars can naturally see portals.

Portals require sentience to use. That way, the natural hazards from the other side do not bleed over. People's worn, carried or held items pass through the portal with no problem. Vortices are a departure from this rule, as they are a naturally occurring combination of energies or elements, and as thus similar conditions surround the portal on both sides of it. Portals are an either/or proposition. You cannot stick your head in to "check out" the other side. You are either on the other side or you are not.

Creation
Portals are created by many sources. Some are simply large magic items, linking the two planes (or two locations within the same plane). Others exist naturally. And powerful entities create others. Most portals, regardless of their nature and origin, provide instantaneous transportation from one plane to another.

Interactions
Using a portal depends on the portal in question. Some portals, such as the color pools of the Astral Plane and ethereal curtains of the Ethereal Plane, require merely stepping through to reach the other side. Other require portal keys, which can take many forms. Portals are also not necessarily two ways. Many kinds of portals exist, after all, such as the following.
 * Time: The portal only functions at a particular time, and only stays open for a set period of time. This time could be as common as every day at noon, or as rare as when the stars of the are in a particular alignment.
 * Situation: The portal only functions if a particular condition is met. One might only open when it rains, or when the wind blows east.
 * Random: A random portal opens randomly, then stays open for a random duration. Some Planewalkers have gone mad trying to find a pattern in a random portal.
 * Command Word: The portal only functions if a particular command word is spoken.
 * Command Item: A favorite in Sigil, these portals only activate when a particular object is held or carried through. It can be extremely common or extremely rare.
 * Two-Way: The most valuable portals allow travel back and forth between two planes.
 * One-Way: This portal only allows one way travel.
 * Variable: These portals send travelers to a variety of different locations, either within a single plane or among several planes.
 * Selective: These portals ban certain objects or individuals from using it. Often, they are based on alignment or race, and deities are most likely to use such a portal.

Discovering Portals
In Sigil, portals are known as "doors" and are extremely common. It is one of the reasons it is known as the "City of Doors." However, finding portals and discovering their keys and destinations is no easy task.

Finding a Portal
Takes one month, and requires a Streetwise or History check (Hard DC). If a planar character using Streetwise, get a +3 to the roll as you can see portals. On success, you have found a portal, but not its key, destination or what kind of portal it is.

Unlocking the Key
Takes one month, and requires an Arcana check (Hard DC). On success, the player has uncovered the key to the portal, and can now use it. Of course, without knowing its destination and if the portal is a two-way portal, this is very risky.

Portal Destination
Takes one month, and requires an Arcana check (Hard DC). On success, the player learns the portal's destination.

Portal Type
Takes one month, and requires an Arcana check (Hard DC). On success, the player learns the portal's type.