Great Vortex

The Great Vortex is a deadly and mysterious weather phenomenon along the clouds of the planet Urvanas.

Background
A blemish within the clouds of Urvanas appears from a cloud city high above as an endlessly twisting vortex whose maw is dozens of miles across, thus creating an enormous empty gap inside the clouds. The gap opens into a wavering, twisting "passage" that leads many miles deeper into the atmosphere. This cyclonic storm is poised over a particular spot along the planet's surface; it doesn't move with respect to the surrounding clouds and winds. Lux tell almost as many stories about the Great Vortex as they do regarding Aato, and some even call it the "Mouth of Zhoh."

Explorers on windriders or similar craft have learned that the only safe way to approach the vortex is from high overhead, and to stay as far as possible from its walls. Those who remain within the center of the vortex's calm eye can travel in relative safety without worrying about the increasing heat or crushing weight of thickening air. However, the further the traveler descends into throat of the vortex, the further the diameter dwindles, and the walls shiver and twist about, making it more and more likely to come into contact with the swirling outer wall. When that occurs, an explorer on a windrider or other craft must succeed on a difficulty 5 Speed-based task to remain in control or otherwise take 10 points of damage and be spun around into the rushing clouds beyond, where survival is difficult. Attempting to pass back in through the spinning wall of the vortex will require the same Speed-based roll.

Explorers and creatures alike who make it to the base of the vortex some 30 miles lower down will discover a tear in reality. Massive structures just visible on the surface beyond the vortex wall, gleaming, tall, and unmelted, in defiance of both the heat and pressure. Nightwatchers suspect these structures are responsible for calling the hole in space, and therefore the vortex, into existence; however, they believe that some malfunction has occurred. They worry that if the hole isn't shut, it'll tear open even further. So far, no explorer sent through the gap has ever returned, though the Nightwatchers still keep looking for new volunteers to try the passage, both within their own ranks as well as from any explorers unaffiliated with the organization. In a few cases, the Nightwatchers have liberated criminals condemned to face the Death Dive and instead sent them down into the vortex.

Miscellaneous
The Great Vortex is actually a one-way transdimensional gate that shifts anything that passes through it to some far away location. That location could be among the sun' other children, such as on the surface of Naharrai, or maybe even in the Phaeton Halo, or it could just be in realms somewhere futher beyond, such as the Thon Iridescence.