Helheim is known as the realm of death and is located in the deepest, darkest and gloomy part of Niflheim, one of the nine worlds of Yggdrasil, in Norse mythology.
It is ruled by Hel, Goddess of Death, and daughter of Loki, and its entrance is guarded by a dog known as Garm.
Helheim and Niflheim are often related as the same world, but this is not so: Niflheim is the realm of cold, ice and darkness, mainly, and, although death and doom are also proper in it, where the latter two specifically occur is in Helheim, the capital of death (so to speak).
In this world ended those who had died of disease or old age, and once one entered it not even the gods could leave, because of the endless, inexhaustible and impassable river Gjöll, which surrounded it.
Of course all criminals will go to Helheim, but for these there are special areas within Helheim.
The Nastrand (corpse beach), also known as Naströnd and Nastrandir, is a hall within the realm of Hel where the souls of vile people, murderers, perjurers and notorious liars will go.
Also in Nastrand as in the rest of Helheim the sun never shines and the ports of the hall all open to the north.
The walls are covered with snakes that all face inward, they spit poison endlessly so it flows in torrents through the hall and fills everything with poisonous vapors. The Nastrand has similarities with hell, according to Christian and Catholic beliefs.
The term "Hell" is a derivative of Hel or Helheim.