Interplanar Travel

The Cosmoloy of Biethal is complicated and varied, from the twilight planes of the Dawnlands and Dusklands to the distant Minor Planes of Outer Chaos. Travel between these planes is possible, though difficult and costly when done by mortals.

Permanent Portals

Portals are the easiet for of interplanar Travel. Permanent portals are varied in appearence, some taking the form of a arch formed from living trees, or an ancient stone altar with a glowing circle on it. Some are always open, some only open on certain circumstances, like the solstice, or when the proper words are spoken. These portals are rare, often in secluded groves or long abandonded temlples. Usually they were put in place by some ancient ritual or dark sacrifice, depending on the location they are going to. 

Summoning/Banishment

With the proper spell and components, anyone has the capability to summon a willing creature from another plane. Most common is for a cult to attempt the summoning of a fiend. In the same manner creatures may also be banished back to their plane of origin with the proper spell.

Spells

Some powerful creatures along with experienced casters have the ability to create temporary portals between planes, or simply send creatures. There are some restrictions on this, its extremeley difficult for fiends, celestials and other beings of the higher and lower planes to portal themselves to the material plane, but they can send weaker agents.  It is easy for many of these creatures it is easier to send smaller beings like imps to the material plane.
Most gods have the ability to manifest on the material plane, but prefer to use avatars instead of going themselves.

Type

Metaphysical, Arcane