Rift

Rifts are one of the most defining features of Mirosia, driving the creation of new islands and bringing new people into the world. These swirling silvery-black portals of energy pull chunks of other planes and those who live on them through.

The Nature of Rifts
Rifts open due to an inherent and not fully understood planar instability present in Mirosia's Weave. Archwizard Ilryser, presumably the most informed expert on the subject, had the following to say in his personal journals:

"Mirosia's precise origins are unknown to me, or to anyone else that I have met. I can only assume, from the best of my research into Mirosia's Weave, that some form of planar instability caused Mirosia to break off from another plane. That instability remains inherent in Mirosia's space-time, causing Mirosia to open Rifts, perhaps in some sort of an attempt to find something that can rectify it's instability.

''Rifts seem to actively seek out places of magical power, artifacts and places of importance. I do not know if there is some form of intelligence guiding this act, or if Mirosia's physics are naturally drawn to the magical power and psionic imprints present upon other planes. Either way, in some sense these kind of energies seem to fill the gap. I've been charting the positions of rifts as new islands emerge for some time now (with a great deal of assistance from the Cartographers' Guild). Notably, as we've accumulated artifacts and people upon the Isle of Mirosia, the number of rifts in our immediate area has decreased. As such, I can only assume that the presence of large quantities of magic and, perhaps, people provides a stabilizing effect on Mirosia's Weave."''

Rifts take the appearance of a swirling silver portal, almost like a mirror, with small black and gray threads intertwined. Their size correlates with the locations that they pull through. A rift will generally form quite quickly, beginning at a small size and rapidly expanding to sizes that can be many miles across. (The largest recorded rift was 26 miles across.) The rifts move gradually, pulling through mass and energy from another plane, sometimes quickly (especially in the case of inhabited locations), taking minutes or even seconds, and sometimes slowly, over the course of several hours. Rifts generally avoid opening in places close to people or even solid matter, meaning there is little risk of suddenly bumping into one that just formed.

Rifts and Planar Travel: No Exits
On a technical level, a rift is a one way planar gateway - it can pull things into Mirosia, but nothing can leave through them - anything that attempts to pass out of Mirosia is instantly disintegrated. This one-way property seems to apply to all planar travel in Mirosia, as no spell, artifact or other effect has thus far been able to allow Mirosians to leave the plane. It is noteworthy that Mirosia has both an Ethereal and Astral plane that remain accessible, but these planes have no connection to others outside of Mirosia. A few spells behave with minor but noteworthy differences in Mirosia, which are listed here:
 * Plane Shift: Cannot target another plane. Will transport to an island from the targeted plane if possible.
 * Instant Summons: Can pull items from other planes. Cannot pull things out of Mirosia.
 * Gate: Cannot target other planes, but can target other islands for it's transport or summon effects, without range limits.
 * Etherealness: Cannot provide access to other planes that would normally be connected to the Ethereal.
 * Astral Projection: Can provide access to the Astral Plane, but other planes (except the material) can not be accessed from the Astral.

Mana Crystalization
The process of pulling things through to other planes can cause one other interesting phenomena - the ambient magic from other locations crystallizes, forming Levia Dragonshards. The crystals create their largest formations on the undersides of Floating Islands, but can often be found elsewhere. Occasionally people have even been found trapped in Levia Dragonshards, indicating the speed at which this process happens.