Nyissa is the southernmost of the countries of the West in David Eddings' book series The Belgariad and The Malloreon. Nyissa is named after its god Issa, who is the snake-god. As a result of their God's totem animal, snakes are deeply respected and admired for their beauty in Nyissa, and are common pets there. The country is ruled by the priestess Salmissra, who is named after the first priestess of Nyissa and love of Issa. At first all the Salmissras were chosen to look exactly like the original, and also given medicines to slow the visible aging process. This was until Polgara turned the latest Salmissra into an immortal snake, who rules them to the end of the series and beyond. Nyissa is located in the swamp and jungles of the southeast of the West, and is largely uninhabited except for its capital Sthiss Tor. Its people have a reputation for being addicted to drugs and similar substances, and they also are masters of poison. (For a list of substances about which they are very knowledge, see Chemicals.)
As reviewed the jungles of Nyissa are not uninhabited; Nyissans exist in very small communities throughout. As seen in The Rivan Codex, or in the early books of the series, the Nyissans suffered a near genocide following their queen's assassination of Gorek, the Rivan King. Salmissra ordered the people to leave their cities and return to the jungle following the Marag invasion, making the Alorn destruction of the nation ineffective as many Nyissans escaped. Currently Sthiss Tor is the only known city.
Salmissra is not only queen, but also the High Priestess of the Serpent God. Thus, when she gives an order, her people automatically obey her, and she'd ordered them to go live out in the brush with the snakes. -Belgarath the Sorcerer