When adventurers travel to other planes of existence, they undertake a 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.
The walls that divide the plane from others are weaker than those of some other planes, making it easier to travel across the multiverse using Orizon as a point of origin. Some “plane striders” make Orizon their adopted home, exploiting this feature and studying the results of the strong magic of Orizon.
Portals
“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 are like doorways, appearing as a clear window or a foggy, clouded passage, and interplanar travel is as simple as stepping through the doorway. Other portals are locations, circles of standing stones, soaring towers, drifting ships, or even whole towns that exist in multiple planes at once or flicker from one to another. Some are vortices, joining an Elemental Plane to a very similar location on the Material Plane.
Spells
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.
Strider's Spark
Awakened by severe duress or strain, the spark of a planes strider ignites to allow these individuals to travel between the planes without expending magic or requiring a portal. Not only does a strider’s spark allow these individuals to travel through a single plane’s planar geography, but it also enables them to travel between distinct planes.
The spark has its limitations, a strider can only travel alone, bringing with them only that which they can carry. Further, striders cannot travel accurately to specific locations on planes, they can accurately tell the plane they are arriving on and its nature, but specific locations are fuzzy until they actually “land.”