Legend holds that Thesnia Trench is the deepest place in the world. This deep sea rift, situated in the Helion Sea to the southwest of the Southern Islands, is thought to have only been seen by a handful of people throughout history, and always by magical means. The legend of Iqira the Seeker describes it as a place where no sunlight reaches, but where strange fish dart among softly glowing corals and sea plants in every color imaginable, which feed off the dead things of the ocean, cleansing it of rot. When she returned from her journey, she declared the trench a holy place of Habbakuk, the god of the sea.
Thesnia Trench is of great importance to the people of Southhaven, who revere Habbakuk as the keeper of their beloved oceans. It is Havener custom to sink the dead into the trench, so their bodies can rest in the holy place and feed the strange and beautiful life there.