Though travel to the planes is usually quite challenging and dangerous, even adventures on the world of Eberron can be profoundly impacted by the planes that lie beyond. This section discusses some unique aspects of the Material Plane and its place in the wider cosmology of Eberron.
Even without planar travel, there are many ways the planes can manifest in an adventure. This chapter examines these potential impacts for each plane using three general categories.
Manifest Zones. These are places where the influence of a plane can be directly felt in the Material Plane. Each manifest zone is tied to a particular physical location on the Material Plane; this is true not only for the Eberron side of the zone, but for the region of the other plane it connects to. So if you live near a manifest zone to Thelanis, it always connects to a specific location in that plane; it’s not simply a manifest zone to Thelanis, it’s a manifest zone to a particular region of the Endless Weald (or any other layer of the plane).
Manifest zones often exhibit one or more of the universal properties of a plane; in a weak manifest zone, their effect might be diminished, and in a strong one, multiple effects might be present. Chapter 4 of Eberron: Rising from the Last War suggests more possible features of manifest zones beyond those presented in this chapter.
Some manifest zones can serve as direct portals between Eberron and another plane (though travel is blocked to Dal Quor and Xoriat). Most portals only open under certain circumstances—often when the planes are coterminous, when the moon associated with that plane is full, or both. These gateways can allow adventurers to travel to another plane— but can also be the source of unexpected, and sometimes hostile, creatures from other planes.
Coterminous and Remote. The planes of Eberron are often depicted as orbiting the Material Plane, reflecting the fact that they move into and out of alignment with it. When a plane is coterminous, it’s aligned; the plane’s influence grows over the entire world, and it amplifies the effects of existing manifest zones. On the other hand, when a plane is remote, its power fades; since the planes are always influencing the Material in subtle ways, their absence impacts the world as strongly as their presence does. Multiple planes can be coterminous at the same time; these planar conjunctions are often related to the interactions of the moons, and characters proficient in Arcana can usually work out upcoming conjunctions.
These planar cycles are intended as plot devices, so DMs don’t need to run them on strict calendar cycles. Instead, use them to suit the story. They can add an interesting mechanical twist to an adventure: because Mabar is coterminous, all undead are stronger! They can drive a villain’s plot: Lady Illmarrow must be stopped from activating the device in three days’ time, when both Mabar and Dolurrh are coterminous— a conjunction that won’t happen again for another century!
It’s ultimately up to the DM to decide when planes are coterminous or remote. If it suits the story for Dolurrh to be remote for the next three days, make it so—just be sure to inform the arcane scholars among the adventurers, who’d likely know such a thing in advance. Other DMs might prefer to have concretely established cycles, which can add their own interesting flavor to an adventure. For example, Mabar is always coterminous on the nights of the new moon closest to the winter solstice, a time known as Long Shadows. On these nights, friends and family gather together and keep lights burning through the night. With this in mind, this chapter does discuss the traditional cycle of each plane, when it’s reliably coterminous or remote—just remember the cycles are there to enhance your story, not limit it!
Artifacts. The planes can be an excellent source of unusual materials, legendary magic items, and relics. Each section discusses a few kinds of items that could come from each plane and its associated manifest zones.