Tytherion

A terrible realm of thirst, of darkness, of dragon-hunted deeps

Tytherion is a dominion in the Astral Sea plane in the World Axis cosmology, native to the Nentir Vale setting of Dungeons & Dragons. Called the Endless Night, it is the dark domain that Tiamat and Zehir share. No light can pierce its darkest depths, and both serpents and dragons haunt its otherworldly wilderness.

First touched upon in the 4e Manual of the Planes, it was further fleshed out in Secrets of the Astral Sea. It bears a passing resemblance to Gehenna and shares some of its features.

Planar Traits

• Type: Astral dominion.
• Size and Shape: Canyon maze about 100 miles across, 800 miles long, and up to 12 miles deep, surrounded by a belt of dry steppes 10 to 50 miles wide; bounded.
• Gravity: Normal.
• Mutability: Divinely mutable. (Deities control their own environs.)
• Alignment: Neutral Evil.
• Corruption: Attacks with the disease or poison keyword gain a +1 bonus to the attack roll. Healing powers restore only half as many hit points as normal.
• Necrotic Affinity: Attacks with the necrotic keyword gain a +1 bonus to the attack roll, and attacks with the radiant keyword deal half damage (ongoing radiant damage is not affected).

A vast maze of canyons shrouded in perpetual darkness, Tytherion is a monster-haunted wasteland where serpents lurk and dragons feed. Sinister temples brood over dizzying precipices, and grim fortresses dot the slopes and spires hidden in the lightless depths below. It is a plane of gloom, of despair, of disillusionment. Here voracious evil gathers its servants and its assets to itself, and hungers for yet more.

Astral travelers who breach Tytherion’s murky indigo color veil find their vessels aground in the dry steppes of the rimlands of a canyon in the heart of a great desert or arid savannah. Tytherion consists of a great canyon, or rather, a canyon complex. The canyon stretches for hundreds of miles. Scores of side canyons, hanging valleys, stony shelves, and mountainous mesas complicate its depths. In many places, canyons cut into other canyons, and the deepest lie a dozen miles or more below the surface.

As travelers descend lower and lower into this brooding black maze, they pass from the desert of the rimlands down through a steep belt of dry, dead brush, where black pines and vicious brambles cling to the slopes. Moving lower still, and the brushland gives way to barren rock, choking fumes, and ash—for in the lowest depths volcanic vents feed sluggish streams of cooling lava that wind through the canyon floors.

Tytherion has no sun, no moon, and no stars. Above its barren mesas a thick cowl of black clouds seethe, lost in the gloom that pervades the plane. The only light native to the plane comes from the evil glow of magma rivers in the lowest depths and the occasional flash of lightning in the black skies overhead. From time to time, violent thunderstorms scour the land, sending torrents of cold water cascading down into the canyons below. Most of the water evaporates by the time it reaches the bottom, turning into layers of steam and vapor that offer the dry brushland a small amount of moisture. How the dead trees and briars grew in the first place, none can say.

Powers of Tytherion

The deities who rule in Tytherion do not pay much attention to their benighted realm. Both Tiamat and Zehir are content to allow their servants—and the monsters native to this awful place—to struggle on as best they can, thereby proving their worth.

Samaragd, the Serpent's Kingdom

The steppes, deserts, and higher canyons of Tytherion are the domain of Zehir. Mortal spirits who displeased Zehir in life are transformed into tormented serpentine monsters. In their mindless anguish, they may yet prove useful by guarding his temples. Mortal spirits who pleased Zehir are rewarded with the opportunity to continue their service to the god of night in the afterlife as darksworn. They remain in their humanoid forms but are granted serpentine features—forked tongues, fangs, lidless eyes—as marks of Zehir’s favor. They serve as priests, acolytes, and temple guards who grovel and chant in the black temples Zehir orders to built in his own honor.

Amun-Atl: This massive stepped pyramid of black stone stands atop an island plateau and is the seat of Zehir’s power. Lesser temples and dark monasteries surround the central ziggurat, which is a city of darksworn acolytes and assassins devoted to their scaly god. Zehir resides in a vast, lightless maze beneath the ziggurat, but he rarely emerges from his den to acknowledge the devotion of his worshipers. His eyes are fixed on his plots against rival deities. Atlathessk, the Seneschal of Night, a yuan-ti exarch who governs in Zehir’s name, runs the domain. Atlathessk demands a steady supply of living mortals to slay upon Zehir’s altars, which means that the denizens of Amun-Atl often deal with githyanki slavers or launch raids of their own against mortal worlds.

Ennek-Vul: The largest of Samaragd’s cliff-face temples, Ennek-Vul can be seen for miles. Its great entrance resembles the yawning maw of a serpent, and the stairs that rise toward it could accommodate a congregation of giants. Said to be the first temple constructed in Tytherion, Ennek-Vul fell out of use thousands of years ago when the Midnight Serpent offered it as a home to his greatest servant, whose name is commonly given as Merrshaulk.

The Labyrinth: Although some sages refer to all the winding passageways beneath Samaragd as the Labyrinth, the exalted of Tytherion use the term more specifically. To them, it refers to the maze of tunnels in which Zehir dwells, coiling and slithering through supernatural darkness while thinking alien thoughts and plotting convoluted schemes. Legend tells that only the most potent magic can create the slightest light within the Labyrinth, and that Zehir shares these tunnels with his most loyal darksworn, who have been transformed into shapes incomprehensible to mortal minds. Supposedly, this complex has dozens of entrances, each so well hidden that only the gods can find it. A few legends suggest that not all the entrances lie within Tytherion; instead, some allow Zehir easy access to the Scales, or even to the Shadowfell and the mortal realm. The approximate locations of only two entrances are known: One lies beneath Amun-Atl, and the other on a cliff face overlooking the Obelisk of Night (see below).

The Murder Pit: This gaping pit near the Obelisk of Night appears to be a great dark pool filled with viscous blackness. Said to be bottomless, the pit connects to none of Tytherion’s other passages. According to legend and to Zehir’s secret dogmas, by listening at the pit, those that use the proper meditative rituals can hear echoes—and occasionally see brief images—of any murder occurring anywhere in the cosmos.

The Obelisk of Night: The Obelisk of Night was present when Zehir first drew Tytherion from the shadows of the Astral Sea and claimed it as his own. This towering monolith of smooth, ink-black stone rises from a crater near the border of Samaragd. Its surface is carved with winding symbols that vaguely resemble Supernal. These sigils resist all magical attempts at translation and seem, on occasion, to shift and waver. Mortals and exalted who study them for too long go blind. Rumor says that Zehir spends days at a stretch examining the Obelisk of Night from within his Labyrinth, perhaps struggling to translate the symbols or contemplating ancient secrets he has already interpreted. No one dares ask which it might be.

The Ravenous Wood: This place is the largest of Samaragd’s copses of dead trees, dried brush, and desiccated brambles. Navigating the Ravenous Wood is nearly impossible, for the thick, flesh-tearing thorns shift deliberately, disorienting travelers and closing off pathways. Zehir’s darksworn believe that the brambles reach out to snag passersby, dragging them within. They also believe that the Ravenous Wood hides the entrance to the lair of a terrible horror that predates or defies both Tiamat and Zehir.

Tabrol-Akla: Several of Zehir’s temples are built on the cliffs of the great chasms that plunge into Tytherion’s depths. Tabrol-Akla has the dubious distinction of being the lowest of these, hovering near the border of Azharul. Unsruuk, the exalted soul of an abnormally intelligent troglodyte, is the temple’s high priest and one of Zehir’s most potent darksworn. Similarly, the other priests who dwell in Tabrol-Akla and the warriors that serve them are among the most formidable of Samaragd, because Zehir’s exalted believe that if Tiamat’s forces ever move openly against Zehir, Tabrol-Akla will be one of their first targets.

• 
  Human sacrifices on a stepped pyramid in the middle of a lush jungle. How original.

Tiamat's Realm: Azharul

Tiamat rules in the lower canyons, haunting the volcanic depths of Tytherion. She claims comparatively few mortal spirits for her own. Those she chooses as her darksworn are left to their own devices in the fuming depths of the plane. The strongest and most clever make themselves into lordlings, ruling over their lessers in the brooding castles of the depths. With little required of them by their dragon goddess, many of these servants of Tiamat continue their former lives of avarice and amass hoards in the afterlife as well. They can be found pursuing their greedy schemes in places such as Sigil, Gloomwrought, Chernoggar, or even Hestavar. Those who fail to win a place for themselves in this heartless order are left to fend for themselves outside the citadel’s walls and become the playthings of the dragons who roam throughout Tiamat’s domain.

Tiamat's Redoubt: The entrance to Tiamat’s lair is a great mountaintop fortress, with five looming watchtowers shaped like the heads and necks of sentinel dragons. The fortress is the gateway to the Caverns of Fiery Splendor, a broad entryway through which even the largest dragon can swoop, swiftly making a journey that would otherwise require hours of wending through the various catacombs. Guarded by Tiamat’s fiercest warriors, the fortress is nearly impregnable.

Caverns of Fiery Splendor: Beneath the deepest pit of Tytherion lies a vast cavern complex of flowing magma rivers and stone ramparts. This sprawling, labyrinthine cavern system is the lair of Tiamat, the Queen of Dragons. The darksworn spirits of evil dragonborn, outcast devils who have sworn allegiance to Tiamat, dark angels, and all manner of draconic spawn fly, crawl, and slither through these vast caves, fawning on the Dragon Queen. Five great wyrms— white, black, green, blue, and red—serve as Tiamat’s consorts and guard her hoard, a collection of treasure that beggars the imagination. Within Tiamat’s lair stand a set of adamantine gates over 100 feet tall. Tiamat does not reveal what might lie beyond them and has never allowed them to be opened.

Yithomel: Within this forbidding citadel, a cabal of Tiamat’s most powerful darksworn spirits rules over a vast region of Tytherion’s middle level canyons. These are the Seven Kings of Yith, mortal monarchs who each devoted their lives to a truly draconic lust for wealth and splendor. Each of the kings competes fiercely to amass more wealth and influence over mortal affairs than the others, with each of them engaged in an endless game of one-upmanship. Dozens of maruts who are bound by centuries-old contracts to protect their gluttonous employers guard the fortress.

• 
  When Tiamat's not in hell, she hangs out here.

Other Inhabitants

Tytherion is also home to a number of outcast devils. Chief among these is the archdevil Geryon, who once ruled Stygia, the fifth hell. The devils of Tytherion are a wretched lot. Some pursue schemes designed to regain the favor of Asmodeus, some continue in their proud rebellion and make empty boasts about wreaking revenge on their infernal rivals, and still others sell themselves as planar mercenaries. Doubtlessly, some of them are also only feigning their disfavor and are secretly serving Asmodeus in their “exile.”

4e doesn't have any yugoloths but if it did, they would dwell here, since it's the closest thing to Gehenna in the World Axis cosmology.

The Crawling Castle: 4e's version of the Crawling City. It doesn't namedrop the General of Gehenna, instead stating the castle belongs to the cambion Vulkur Vaal, also known as Vaal the Flayer.

Hopelorn: The stronghold of the lich-lord Melif has also been moved to Tytherion.

The Scales: The astral archipelago of Tytherion is a dark and unpleasant place for exalted of Tiamat and Zehir to hide without leaving the plane.