The Ecology of Manifest Zones

The key to understanding Manifest Zones in Eberron is that they are not placed randomly. Almost always, a manifest zone of considerable size is located in a place with natural phenomena echoing that trait: Sharn is located in a place with high plateaus and strong winds, Greenheart in the Eldeen Reaches is a vast untamed wilderness, and Frostfell is a literal tundra. One possibility is that the Manifest Zone causes such regions, which is partly true; but we also have evidence in canon that the opposite is true. Valin Field, in southwestern Thane, became a manifest zone to Shavarath after a ritual and a terrible massacre, while a similar location called Tamor Gulch has been the traditional location of bloodsport for years. The Aerenal city of Shai Mordai is built on perhaps one of the largest Manifest Zones for Irian in Eberron, while the Gloaming in the Eldeen Reaches is growing.

This is my personal theory on how Manifest Zones in Eberron work. They are originally created during the coterminous phase between a plane and Eberron. The coterminous phase does not fall on all of Eberron at once; rather, the coterminous phases have a long line or shadow, similar affected area of an eclipse.

Within the shadow or coterminous area of a plane, the entire region is said to be similar to a manifest zone. Some areas will not be affected because they are shielded for some reason - for example, areas of strong light and joy are shielded from the full effects of being coterminous with Mabar - but the region in general is almost like a manifest zone, or a thousand little manifest zones.

As a plane moves out of its coterminous phase, most of these tiny manifest zones disappear. Some, however, hold on, encouraged by their locale. For example, a tiny manifest zone to Fernia might remain in an oven or fire pit after the heat of the Fernian summer has passed.

As the manifest zone remains, its influence grows, which means the manifest zone grows. However, if it were to lose the thing anchoring it to a region, its influence would wains. The Fernia manifest zone could cause a fire that burns down the bakery; for the brief time that the bakery was on fire, the manifest zone would grow, but once the fire was destroyed, the manifest zone's hold on this plane would be lost.

Most of the tiny manifest zones are extinguished in this way, but the larger a manifest zone becomes, the harder it becomes to extinguish.

The second thing to keep in mind is that there is only a limited amount of space that can be occupied by manifest zones in Eberron. Either because of the Manifest Zone cycle, or because the different types of zones cancel each other out, or for some unknown factor, most manifest zones stay long term in specific locations, and even as some grow, others shrink.

I divide Manifest Zones into several specific types.

Sybaris Manifest Zones are the largest, most powerful manifest zones. They act as a minor Gateway to their corresponding plane, and there is only one for each (except of course Dal Quor). The link to Shai Mordai in Aerenal has been the Sybaris Manifest Zone for around thirty millenia, growing slowly with the growth of the Court. A Sybaris Manifest Zone is just over 70 miles in diameter. The Sybaris Manifest Zone to Fernia is in Xen'Drik, while the one to Risia is in the Frostfell, and the one to Daanvi is in Sarlona. The rest tend to be located in Argonnessen, or perhaps in the ocean.

Greater Manifest Zones are generally 1-5 miles in diameter, though some larger have been recorded. These are the manifest zones, like the one in Sharn that most people think of, and they are usually the ones noted in canon. They act as minor Gateways to their corresponding planes in the weeks before and after a coterminous period. There are roughly 144 Greater Manifest Zones for each plane, except Dal Quor.

Lesser Manifest Zones are between 150 - 2,200 feet in diameter. They can act as a Minor Gateway for a fraction of the time that their corresponding plane is coterminous, and are strong enough to act as a conduit for Eldritch Machines. There are over 1,725 Lesser Manifest Zones per plane, except of course for Dal Quor.

Finally, Least Manifest Zones are 13-150 feet in diameter. They have only minor properties associated with a manifest zone, though they gain dramatically in strength to that of a Lesser Manifest Zone during coterminous phases. There are over 20,700 Least Manifest Zones per plane.

Phantom zones are no more than 13 feet in diameter, and only appear in the shadow of a Planar convergence. Uncounted numbers of them appear in the affected area, only for most of them to disappear shortly after the coterminous phase.

Due to Dal Quor being missing, the continent of Sarlona is home to two unique types of Manifest Zones. The first, Wild Zones, seem almost non-existent most of the time, and are quite small, but during Coterminous Phases of the correspondent plane bloom into actual portals to the planes. This type of Manifest Zone can be very dangerous, and access to them is tightly controlled by the Inspired. The second type of Manifest Zone native to Sarlona are the Aukaraks or "Reality Storms". Aukaraks are the leftover manifest zones from Dal Quor, from the Sybaris zone to the least Manifest Zones. They can't attach themselves to the world properly, so instead the Aukaraks cause ripples in reality, coming into being and disappearing much like the storms from whence they take their name.

In the deep and currents of the oceans, some Manifest Zones have been known to wander, attaching themselves to a cycle or current rather than a location. Merfolk and others take advantage of these wandering Manifest Zones to set up locations and pods. Wandering Manifest Zones make sea travel a little bit more dangerous.