The Plunge

Far below the icy caverns of Lower Deep, there is a point where the rock stops and opens into a chasm which stretches farther in all directions than the eye can see. This chasm is filled with a vast, deep ocean, frozen over with a layer of ice. This forbidding landscape is known as the Plunge and is truly the bottom of the inhabited world.    

The Icy Expanse

The Plunge is completely covered in a layer of ice. This ice varies in thickness, from a paper-thin sheet to several feet thick. Any creatures which travel across the ice must be extremely careful to test the ice where they step, or risk falling into the cold, dark depths of the ocean below. The ceiling above also varies in height, ending anywhere from a couple hundred feet to far below the ice. Most of this expanse is open and can be traversed with little concern for being lost within winding passages. Instead, one must fear losing their way because everything looks the same. Many travelers have ventured across the Plunge, only to disappear forever or reappear many miles from where they entered.  

Life in the Dark

Despite the lack of sunlight and extreme cold in the Plunge, it is actually teeming with life. Far below at the bottom of the ocean, communities of invertebrates and other small organisms congregate around two different kinds of phenomenons.   The first of these phenomenons is the hydrothermal vent. Here, superheated volcanic gases escape from the core of the planet, forming small chimney-like rocks. The water surrounding these formations is much warmer than the surrounding ocean, and attracts all manner of small invertebrates and plants. These organisms feed on the nutrients and molecules which seep from the rock stacks. Other, larger organisms feed on them, creating small ecosystems in the vicinity of the vents.   The second is known as a cold seep. Here, supercold and dense forms of carbon such as methane sink together in pools below the water. While nothing can live inside such pools, organisms on the edges of these pools can feed on the pool's contents and subsequently feed other organisms.   Most organisms in the Plunge rely on bioluminescence to light their way. Some use it to lure prey, while others use it to confuse predators.   There are whispers of massive creatures living in the Plunge which can be seen as massive shadows lurking just below the ice. No Deepfolk have ever seen these creatures face-to-face, or none have ever survived such an encounter.  

Yzteus

The Plunge has its own deity in Deep folklore. This deity is known as Yzteus. Yzteus is depicted as a massive, roiling tangle of tentacles surrounding a central eye. The eye itself is also massive and painted in the same manner as the other Deep deities. Yzteus is not worshiped by many Deepfolk, as many do not come close to approaching the deity's domain. It is greatly feared in the same manner as the Dark deities of the surface world, particularly Brantis, the void. Yzteus is considered its Deep counterpart, as most Deepfolk associate the Plunge with a bottomless, freezing ocean.   Many tales speak of foolish Deepfolk venturing onto the ice of the Plunge, only to be snatched from below by the long, barbed tentacles of Yzteus. This is often used as a warning to the young of Lower Deep, scaring them from the idea of wandering too far down and finding their way to the Plunge.   It is said Yzteus was not created by Khelmeeshe, and instead came into being quite spontaneously when Galactus and the Plunge itself were created.  

The Plunge in Deep Culture

The Plunge is feared by most Deepfolk. Most find no use for the endless expanse of rock and ice, and wish to avoid the dangers which come with travelling across it. It is mostly ignored by the folk who live in Upper Deep and the Deep Main, as they almost never venture far enough below to reach it - in fact, some more secluded tribes do not even know of its existence. One must first traverse Lower Deep, which is a perilous journey unto itself and is not taken lightly. If one has traveled that far, it is undesirable to venture still further for much risk and no reward.   Those who live in Lower Deep, however, have a slightly different relationship with the icy swathes below their feet. Some more intrepid and experienced explorers have devised safe ways of travelling across the Plunge as a faster way to reach other locations in Lower Deep. Some of the more frequently used paths are marked with ropes, stones, or carved symbols in the ice. Near some popular crossing points, enterprising Deepfolk set up small taverns or rest stations stocked with food, drink, and other supplies. Some of these places rent or sell sleds, which folk crossing the Plunge can use to move more swiftly across the ice. These are also quite useful when accidentally crossing a thin stretch of ice, as they float in water if the ice breaks through, helping the rider to avoid plunging into the freezing ocean and drowning or becoming prey to some unknown beast lurking in the depths.  

The Plunge in Surface Culture

Surface folk do not often learn of the Plunge unless they have a particular interest in the distinct layers of the Deep or in the folk of Lower Deep. Because many Deepfolk fear or entirely disregard its presence in most circumstances, they do not often speak of the Plunge, especially around strangers. Those that know of the Plunge typically find it either incredibly unsettling or quite fascinating.   Those who find it unsettling typically do so because they feel it is associated with Branis, the void, who is universally feared or hated by surface folk. They feel that the Plunge may have no bottom at all since exploration of the ocean is very limited and nearly impossible. The stories of Yzteus only serve to reinforce this belief, and many surface folk hold the superstition that to venture onto the ice of the Plunge is to invite death. They believe that stepping onto the ice will result in either immediately falling through and drowning, or being snatched by some creature of the Plunge or Yzteus itself.   There are a few known places in surface oceans which reach so deep they are believed to connect to the Plunge. There is one located somewhere in the Jade Sea, as well as in the Grey Ocean and the Northern Ocean. These look like massive, black sinkholes that seemingly have no bottom. No explorer has ever been able to follow such holes to their end, given the immense water pressure and cold from venturing so deep, but the aquatic folk such as Tritons and sea-elves avoid such sinkholes because in their stories they are the birthplaces of many terrifying sea monsters.