Lake Nirthran (also known as the Dying Sea) is the largest known body of water in the Darklands level of Sekamina. Much of it is situated beneath the Inner Sea and is fed by the Braid. In the same way that the Inner Sea divides Avistan and Garund, Lake Nirthran divides the drow empire to the north from the ghoul lands to the south.
The lake bed drops sharply from the shore, quickly reaching several hundred feet in depth within a few miles. The centre of the lake is much shallower due to a gravitational anomaly in Golarion's orbit and the erratic orbits of the planets Akiton and Castrovel. The floor of the lake bulges up here and the water averages only fifty feet in depth. There are also several islands in the central section.
The eastern region of the lake forms an immense crescent around where the Isle of Kortos is found on the surface. Water rains down here from the Inner Sea, where a current takes it westward. At its western edge, the water churns violently as it flows through numerous weaknesses in the rock into the Sightless Sea in Orv below.
The lake is fed by Darklands trickles, streams, and rivers from all over this region of Sekamina and Nar-Voth. The most well-known of these streams is the Tenebros River, which has its origins in the countless caverns below the Candlestone Caves in northern Andoran.
The drow maintain two ports on the northern shores of Lake Nirthran: Telderist and Delvingulf. On the lake floor between them (and slightly farther south), lies the skum settlement of Cold Momugado, while hundreds of miles to the southeast is the mysterious skum enclave of Ulat-Kini. Although the ghoul city of Nemret Noktoria is not located directly on the Dying Sea, it is close enough to its southern border to have a major influence.
The depths of the lake are home to numerous species of giant fish, including luminous, primordial sharks, the eyeless leviathans known as the faceless whales, and a colossal, evil sea serpent known as the Mourning One. The central islands are inhabited by skum, and the strongest of their tribes live in the settlement of Cold Momugado where they worship a massive tentacled horror named Shumbauth who is said to live in the depths of the lake's western reaches.
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