Death in Traykon is not as simple as "go toward the light, John." When a character dies, (is reduced below -10 hit points, suffers ability damage that results in a 0 Constitution, or certain spell effects) the characters soul is shunted into the Shadow World. Once in this state, the soul of the character is inevitably drawn toward either the plane of their deity or a plane of a matching alignment. This process of soul migration normally takes 2d8 linear days. During this time, a character's soul may be coaxed back into its body.
Coaxing a soul to re-inhabit its body normally requires the assistance of an outsider (a creature not native to the material world). Intrepid individuals can do a calling to try and attempt contact with one of these powers. Once contacted, a bargain can be reached with the outsider for the service of finding the soul and coaxing it back to its body. This kind of bargaining is never cheap. Evil outsiders often will bargain for the rights to the soul in question. Good outsiders (who hardly ever answer the calling anyway) will often perform the service for the sacrifice of something of great personal worth. Agents of a particular deity may also perform the service of finding the soul but their tasks are always quests for their deity. If a bargain is reached that would require the soul's agreement, then the soul must agree before it is brought back to its body.
Once a bargain is made, the outsider simply searches the Shadow World for the traveling soul. If the soul is still in the loose in the land, the outsider will retrieve the soul and bring it back to the body. In order for the soul to remain in the body, the body must be in good condition (wounds will need to have been healed magically, poisons will have to be removed) and the body must be capable of supporting a living soul. (Characters who have died of old age or bodies that are too badly damaged to support life cannot be reanimated this way.) Once the soul is brought back into the body, the individual must make a Willpower save (DC 5) to be able to reattach to the body.
There is always a danger of some rogue soul taking the body before the correct soul has reattached. A soul can fight for control of its body by making an opposed Wisdom Check against the possessing spirit. A successful check means that the trespasser is expelled forever, a failed check means that the trespasser takes control of the body and consigns the body's soul to oblivion. Often, a possessed persons fellows will not know what has transpired until it is too late to reverse the process. Only a wish or miracle will bring a character back whose body has been usurped in this manner. Although an outsider will not necessarily tell a group of their friends possessed state, they will never arrange such a switch as that invalidates their bargain.
Another danger of using this method is the dangers inherent in the calling. Many entities exist in the Shadow World who can benefit from capturing lost souls. Deities like the Wild Hunt will often sense the calling and go hunting for the soul in question. When the Wild Hunt captures a soul that has been bargained for, the soul inhabits the body of one of the Pack. Only by convincing a Druid to bargain with Wild Hunt for the soul can the soul ever be returned to its body. When the Wild Hunt bargains for souls in this manner, another soul must be substituted. The other soul must be willing and devoid of magical compulsions. If the member of the Pack with the character's soul is killed before the soul is released, the soul is immediately confined in Ulvanic Keep, where the god Ulan dwells.
There are many other hazards to a soul on the journey. Many fiends and devils aspire to divinity and often capture stray souls to power their "godhood". Those who died having no particular divine attachment or even a strong opinion as to their position in the universe (weak tendencies in their alignment) have a chance of becoming trapped in the shodowy void. Trapped souls slip close to the material plane and become Ghosts, hence the often used term Lost Soul. Furthermore, there are natural hazards that can befall a soul in the Shadow World. Free floating Vortexes, Spatial Rifts, and solid "demi-planes" can always usurp a souls passage. With the number of deaths in Traykon, there is maybe a 1% chance that something unexpected happens to a soul, but the DM is the final arbiter of such things.
Magic may of course bring a character back to life as stated in the individual spell descriptions. Many deities will demand certain concessions for the ability to raise the dead. Deities like Ina Po and Ulan will only allow their priests to raise characters from the dead rarely and must always express dire need. Deities like the Unnamed One will only allow it under very, very special conditions (these deities prefer the individual be brought back via undeath).
Ulan actively searches for the souls of very pious individuals and deposits them directly on the plane of their deity. Only characters who devoutly follow a deity and are capable of casting divine spells draw Ulan's direct attention. His own followers are gathered up and taken to the Ulvanic Keep in the Plane of Shadow regardless of their ability to cast divine spells. Being devoted to him is enough for him to be attracted to their soul. Ulan's followers cannot be "coaxed" back from the dead. Also, Ulan's priests will use magic to retrieve someone from death, however unless the character is a follower of Ulan the person comes back with a divine proscription upon them to undertake a quest for the deity. Those who fail to do so within 1 year of being returned simply have their soul reclaimed and instantaneously die. Until this quest is taken, the soul can not be brought back again if the person dies as it becomes the property of Ulan.