Petitioner

Petitioner was the term applied to a dead person's soul that made it in some way or another to a plane of existence other than the Material Plane.

"Petitioners don't care about whether they are killed in the name of the Blood War or in the name of justice. They're just deaders."

- The Declaration of the Ring-Givers

Becoming a petitioner
"I don't see it as death so much as a chance for a new life."

- Aroukis, a petitioner of Apollo sharing their view on being a petitioner.

Upon dying, a mortal's soul was transported to the Fugue Plane. Once there, these souls counted as petitioners but didn't have the attributes of one yet. They became full petitioners after entering the plane of their respective deities.

Other petitioners received judgement from Kelemvor, the assigned arbiter of the placement of the dead. The standards by which such judgement was made were based on whether or not a mortal followed their deity, which deity they chose, and how honestly they lived according to its ideals during their lifetime. If a petitioner did not have a specific patron deity in life (most mortals were polytheistic), they were taken in by the deity who was most closely aligned with their moral and ethical outlook. Those who never paid homage to any deity, or betrayed their god, were deemed Faithless or False.

Normal Petitioners
Normally, a soul of a dead mortal went to the Fugue Plane. Once there, it waited until the deity it followed during its lifetime or an agent of the same came and took it to its final destination, that is, the divine realm of the deity. In the deity's realm, the petitioner became a full petitioner with all the attributes of one.

Attributes
A normal petitioner served its deity and interacted with their realm in varying capacities, based on the nature of the deity they served. Petitioners didn't usually remember their previous life, though there was some evidence to suggest that they retained strong emotions connected with those they knew in life, such as past lovers or family members. If their loved ones followed the same deity, or pantheon, they could be reunited.

Some petitioners were remodeled upon entering the realm of their deity. For example, followers of an elven deity took on the form of handsome elves with exaggerated, fey-seeming features, even if they weren't elves in life. A similar thing occurs with petitioners of the dwarven deities, appearing as sturdy dwarves. Barring resurrection, a petitioner could not leave the realm of their deity, though allied deities allowed their petitioners to mingle with loved ones who served another deity. While most resurrected petitioners didn't usually retain their memories of their time being dead, Fflar Starbrow Melruth retained vague memories.

Duties
As mentioned above, a petitioner served their deity in varying capacities, based on the nature of the deity. Some had a more relaxed afterlife, while others were called upon to defend the realm. Petitioner pursuits could also be similar to those it had in life. For example, petitioners of Oghma would pursue knowledge in the vast libraries of the Hall of Knowledge, petitioners of Tempus engaged in battle, and those of Arvandor spent their days feasting on its bounty and communing with its nature.

Unclaimed Petitioners
There were few beings, whether deity or mortal, who wished for a soul to go unclaimed. The gods greatly desired mortal souls, and some would try unorthodox tactics to claim even those that would rightfully go to other gods, let alone those no one else wanted. Lurue the Unicorn Queen for example attempted to find the souls of those who died alone in forests and other wild places, attempting to take them to her realm if no one else would. Deities of the dead would even try to claim souls by conducting certain funerary rites. Even so, the gods had standards for which souls they would claim, and those deemed unworthy by whatever standard they applied would not be collected.

Faithless
The label of "Faithless" referred to the soul of a deceased individual who had no patron deity. This meant that the soul in question lacked any true personal attachment to any deity, which could be for different reasons. For example, only paying lip service to one without ever truly believing would constitute faithless behavior.

This could also mean that the soul in question never believed that deities existed during their lifetime, having firmly denied their existence, though this was rare given that deities were very active forces on Toril. Even this, however, was not necessarily the stumbling block it appeared to be. By necessity all druids possessed patron deities for example, but not all distinguished the divine forces from nature itself.

Even someone who had no patron deity beforehand could choose one at the time of their death, even if they never displayed active interest in any deity. One who refused to take a patron even at this moment was truly faithless, and it was for they that Kelemvor reserved his infamous punishment.

All Faithless souls received the same sentence from Kelemvor. If no deity came to claim the soul in question (which depending on the god took somewhere between a day and a tenday), he disposed of them in a process that itself took between one to ten days. Such a soul could still be resurrected or reincarnated before Kelemvor was finished dealing with them, after which they were used to form bricks in the living Wall of the Faithless around his City of Judgement, held with a supernatural greenish mold that prevented escape and broke down their soulstuff until all consciousness was dissolved into the plane. Only divine intervention (such as through a miracle or wish spell symbolizing such) could save the soul at that point.

False
The label of "False" referred to the soul of a deceased individual who intentionally turned from a faith they believed in. This did not mean that all who had a change of heart were branded as false, but to actively change religions haphazardly or quickly was likely to garner one a reputation for weakness of faith and risk the label. These false souls were judged and punished according to their deeds in life.

The punishment was enacted by Kelemvor and Jergal but the content was determined by the deity the petitioner swayed from. It always included an assignment as the eternal labor force in the City of Judgement. The punishment ranged from something light, such as to work as an escort, to the sort of torture that demons were incapable of envisioning.

A False couldn't be resurrected without the consent of the deity from whom the soul swayed in life and only after that deity negotiated with Kelemvor.

Like the Faithless, the False were also capable of leaving the Fugue Plane, at least in theory.

Fiends
Small enclaves of baatezu devils existed on the Fugue plane and were allowed, by contract with Kelemvor, to negotiate with souls while they were there. While not permitted to hurt or trick them (normally), they could explain the situation they were in and bargain with them. The baatezu sought souls that could be used to create lemures, the lowest devils, and generally only particularly wicked mortals could be subject to the transformation.
 * Devils:

While not the most appealing of offers, souls who for whatever reason feared for their future in the hands of their own vile deities might be tempted to consign themselves to the Nine Hells. Early or automatic promotions could be haggled for depending on the power of the soul and outcome of its bargain, as could other benefits like the performance of devilish services against still-living enemies or even aid for friends and family. The conversion rate was low for the baatezu, but enough souls died across Faerun that making the offers was still worth it, and just because it was illegal didn't mean some baatezu wouldn't steal souls.

Before transformation the average hellish petitioner, sometimes called a "soul shell", were ghost-white shades, although not insubstantial wisps. They were (as much as other petitioners) beings of flesh and bone, and in fact slightly rubbery. The term referred to the fact that they were mere shells of their former selves, disheveled, terrified and as wounded as they were in life. After the paperwork was done, a program of torture was enacted to strip away their humanity and individuality and drain them of divine magical energy before what was left of the quivering husk was dumped in a putrid processing chamber and reborn as a lemure.

Demons sometimes attacked the Wall of the Faithless to harvest from it and occasionally raid the City of Judgement to kidnap some of its denizens. Kelemvor would tolerate to this a point - but would move against the demons, with help from Jergal's servants as well as Baatezu, when collateral damage became too high for him to endure or if his divine servants were directly at risk. Sometimes after an attack he would counter with his own sorties into the realms of the Abyss that they came from. Petitioners who were brought into the Abyss became manes.
 * Demons:

Malicious mortals spirits that came to the Barrens of Doom and Despair or the Blood Rift were reborn as soul larva, the currency of the fiendish planes who could be used to create other types of fiends, including lemures or dretches. Kelemvor might see fit to impose this form on an unclaimed soul before casting the squirming worm into the dust.
 * Larva:

Unusual Petitioners
Worshipers of the gods Tyr, Torm, and Ilmater became lantern archons when they died.

Petitioners of Brightwater became creatures highly similar, if not identical to, bacchae, revelers caught between human and bestial natures.

A vhaerath was a special type of petitioner who followed Vhaeraun.

Petitioners of Auril and Talos took on almost elemental forms, appearing as cold spirits for the former and sentient lightning for the latter.

Souls of certain planes were known to take on the forms of animals. Petitioners of the House of Nature initially appeared as they did as mortals, but over the course of centuries gradually took on more bestial features until they became Celestial creatures. The evil gnome god Urdlen turned his petitioners into small, blind moles with adamantine claws. Malar, and to a lesser extent Umberlee, transformed their petitioners into particularly fierce and primal versions of normal animals. Like the fiends, Malar also stole souls from the Fugue Plane before forcing them into innocuous animal forms for his own petitioners to hunt.

Unusual Attributes
Some types of petitioners possessed abilities unusual for their kind.

Certain types of petitioners were able to leave their home plane. These included those that became members of outsider races, such as lantern archons, larva, lemures, and manes, and others like the vhaerath, who could leave Vhaeraun's realm of Ellaniath.

Certain types of petitioners retained the abilities they possessed in life, although not necessarily the context for how they had them. These included petitioners from the House of Knowledge and the vhaerath.