In the mythology of the Mabuiag people of the Torres Strait, Kibu mythology is the mythical land of the dead, believed to exist over the horizon far to the west. The correct full term is Kibukuth Horizons End. The basic meaning of the word kibu is midpoint of an upright broad object, such as small of back, mid-slope of a hill, and horizon, which is the midpoint of the universe, between the bottom part which is the earth (apagœwa lower-ground, or arkath pit), and the top half, which is the sky (dapar). The reference to Kibu, the land of the markai (the spirits of people who have travelled to Kibu after death) is a specialised, religious use of the word. Traditional Torres Strait religion can be characterised as totemic and ancestor worship, and as such the markai are the ancestors, and are specially revered. The ancestors are with the augadh totem, and the augadh generates the buwai clan/moiety, and the markai ultimately has a direct relationship to the augadh, though not necessarily being seen as being the augadh.
In the traditional mythology, the world (arkath hole, apagoewa underfurrow/ditch/garden) is at the bottom of a sphere, with the sky (dapar) above and around it. The markai live in Kibu, the main gateway of which is in the west (Kibukuth Horizons End). However, the markai often come back to visit. The land of the markai actually surrounds the world, so markai can be seen passing from east to west as well as west to east, coming down from the sky, and sometimes even coming up from under the ground via Apangab Netherway, Underway, the mythical pathway under the earth used by markai and others, such as dhogai long-eared witch women, maidhalaig magic-men, and others to travel under the earth and the sea from place to place.
Before becoming markai, the spirit of the dead person is called mari. Mari are the spirits of the dead who have not yet passed to the other side. The passage to the other side is made on the sand banks just west of Boigu, in north-west Torres Strait. At Boigu, the mari either leave a sign or otherwise talk to the mariumulaimoebaig spirit talker, to let people know how he or she died, and if he or she was murdered (and if so, who killed them). This is done where the cemetery is at Boigu, just west of the village.
In the passage over to the other side, at the sandbanks west of Boigu, the mari, which is black (kubikub) just as in life, becomes white (gamulnga) (this is a belief common to many Pacific and Australian peoples). Therefore, when Asians and Europeans visited Torres Strait, they were at first believed to be markai returning. In the modern language, markai is still often used to refer to Europeans, though no longer to Asians. However, this is considered to be impolite, and the correct term is either Yurupau Moebaig European or Gamulmoebaig (Light) Coloured Person. One favourite means of transport of the markai is the markaigub spirit wind, that is to say, waterspouts, which appear in the North-West Monsoon season, the favorite time for the markai to come to Torres Strait. As this was the season the Makkasarese and similar Indonesian fishermen came to Northern Australia, they were associated with the markai.