Seadarias

In the depths of The Sea of Tears, the Triton city of Zeyshel is visible by the faint yellow-green glow of the lights that guide people through its streets. The very observant and well travelled might notice a similar-hued light occasionally lighting the room in the homes of Aeschira and other Drow settlements. This shared light source is the result of a long-standing trade between the Triton and Drow people, and one of the chief exports of Zeyshel: Seadarias.
A form of jellyfish with a natural bioluminescence, Seadarias have long been a creature farmed in enclosures near the Triton settlement bounded by huge nets woven from seaweed and rope made from other plant fibers. By supplying them with particular species of crabs and small fish the Tritons have learned to adjust and augment their light. Typically they aim for a moderately bright, cool chartreuse which works well both underwater and underground, but some Seadarias are kept separately to produce a small variety of other colours and intensities. What makes them especially unique is that the light produced by the Seadaria lasts for a full month after death. When they are harvested, simply wrapping the bulb of the body around a stick will create a torch that will glow gently for weeks at a time.
The Seadaria themselves have a spherical body about the diameter of a large serving plate or a round shield, with feather-like tendrils that drift beneath them for dozens of meters. Naturally, their body is almost completely translucent with the faintest blue tint around the edges and linings. The Triton first began using them as torches when some villagers found a small valley in the seabed full of Seadaria corpses, still glowing faintly after a school of them had floated past and eaten a particularly poisonous batch of shellfish. Now they are a major part of the Triton economy, and a key source of light for both the people of Zeyshel and the Drow cities.