We know from Legends & Lore that when mortal characters die, their souls spend 3-30 days traversing the Astral Plane to reach the Outer Plane associated with the character's alignment to either spend eternity in rest/torment (for those races with souls - humans, dwarfs, gnomes, halflings, and half-elves) or be reincarnated (for those races with spirits - elves, half-orcs, humanoids). L&L goes on further to state that "The road through the Astral Plane to their destination is clearly marked for the dead, but it is not free of peril. Some monsters roam the ethereal and astral planes at will, which is why burial chambers often include weapons, treasure, and even bodyguards to protect the soul on its journey."
This suggests that for living characters who have projected onto the Astral Plane that encountering and interacting with the souls/spirits of the recently-deceased should be not only possible but fairly common - surely more common than encountering other plane-traveling mortals, gods, etc. However, the encounter tables for the Astral Plane in the DMG and L&L (which I believe are identical to each other, but I haven't checked them side-by-side to confirm) do not include this possibility; neither is it mentioned in the Astral Plane write-up in Dragon #67 (or, for that matter, in TSR's post-Gygax Manual of the Planes). This might have been intentional - that even though the souls are traversing the Astral Plane in the same manner as mortals, they are of sufficiently different substance that interaction is not possible - but I don't think so: the cosmology of the Astral Plane suggests that projecting mortals and transiting souls should be able to interact with each other. Therefore, my suspicion is that this was simply overlooked when the encounter tables were being compiled, and unsurprisingly that error was carried forward in Roger Moore's article (which, when compared to the info in the back of L&L, doesn't actually add any new concepts or ideas, but rather just piles a bunch of mundane detail (e.g. effects of zero-gravity on every spell) and commentary on top of the existing conceptual framework).
Therefore, in order to rectify that oversight and hopefully bring more color and interest to the Astral Plane, to restore some of its mystical role that gets obscured by Roger Moore's relentless focus on zero-G physics, I propose the following:
Encounters with the dead on the Astral Plane
The chance of an encounter for characters traveling on the Astral Plane is doubled (from 1-in-20 to 1-in-10), but 50% of all encounters are with a group of dead souls/spirits in transit from the Prime Material Plane to one of the Outer Planes. There will be 1-100 souls/spirits in each group. For convenience's sake, all members of each group can be assumed to be of the same race and alignment:
14-15 Demi-human (1-2 dwarf, 3-4 gnome, 5 half-elf, 6 halfling)
17-20 Humanoid (1 bugbear, 2 centaur or satyr, 3 ettin, 4 giant, 5-6 gnoll, 7-8 goblin or hobgoblin, 9 ixitxachitl, 10-11 kobold, 12 kuo-toa, 13 lizard man, 14 locathah or merman, 15 ogre or troll, 16-17 orc, 18 sahuagin, 19 troglodyte, 20 other)
Alignment (for Humans - demi-humans and humanoids as per standard racial alignment)
1-3 lawful good
4-7 lawful neutral
8-10 lawful evil
11-12 neutral good
16-17 neutral evil
18 chaotic good
19 chaotic neutral
20 chaotic evil
Most of these souls will have been mundane 0-level types, but there is a 10% chance that any group of humans encountered includes 1-3 former character-types:
4-6 fighter (1-5) or cavalier (6)
0 other (monk (1-3) or bard (4-6))
Roll 1d8 for level; on a roll of 8 roll 1d8+7, on a roll of 15 roll 1d6+14
Any group of demi-humans has a 25% chance for 1-3 character types:
4-8 other (as appropriate by race)
Any group of humanoids is 5% likely to include 1-2 shamans or witch-doctors.
Souls and spirits have all of the same characteristics and abilities as they had in life. They have the full hit points they had prior to the event (sickness, accident, combat, etc.) that caused their death, and those with spell-casting capability will have their full complement of spells. However, they are only equipped with those items that were included with their funeral (buried, burned, or otherwise left with them): those who did not receive a proper burial or funeral will be naked, and any item that was left with the body but is stolen or taken away before the soul reaches its destination will disappear from the soul's possession.
These traveling souls and spirits will generally seek to avoid contact and hurry along their appointed route (which is visible to them, but not to living mortals). However, some may be willing to tarry and speak. They may be willing to tell the story of their death, and may ask for news of the mortal world, or may be confused or worried or sad, or may plead with the characters to Raise or Resurrect them. Some may wish to leave their appointed path and travel with the party, but those who do so will still find themselves inexorably drawn away within 1-6 days and in any event are unable to exit the Astral Plane to any plane other than their appointed Outer Plane.
Some souls and spirits may be hostile and attack. Some may think that if they are able to defeat a living mortal that they may travel back along its silver cord to possess the traveler's earthly body and be reincarnated.
Note that any deceased soul or spirit that is "slain" on the Astral Plane before reaching its appointed Outer Plane is permanently destroyed - that character cannot later be Raised, Resurrected, Reincarnated, or contacted via Speak With Dead.
Psychopomps: A psychopomp is a powerful immortal being that guides and defends deceased mortal souls and spirits in their journey across the Astral Plane. There is a base 5% chance that a psychopomp will be accompanying any group of souls or spirits encountered, 10% if the group includes a cleric or shaman/witch-doctor of 1st-4th level or other character-types of 5th-8th level, 25% if the group includes a cleric or shaman of 5th-8th level or other character-types of 9th level or higher, 50% if the group includes a cleric of 9th-11th level, and will always be accompanying any group that includes a cleric of 12th level or higher.
The psychopomp will seek to prevent any outsiders from communicating or interfering with its charges (and vice versa), and will immediately attack anyone who tries to remove any of them from the path to their destined Outer Plane.
The particular psychopomp present is determined by the alignment of the group of souls or spirits being accompanied:
Good-aligned souls and spirits: 1-3 astral devas
Neutral-aligned souls and spirits: Anubis
Chaotic good or neutral groups including one or more fighters or barbarians: 2-8 Valkyries
Evil-aligned souls and spirits: Hermes, who hands the group off to Charon (1-2) or a charonadaemon (3-6) at the River Styx
For the World of Greyhawk setting:
Good-aligned souls and spirits: 1-3 astral devas
Neutral-aligned souls and spirits: Celestian
Evil-aligned souls and spirits: 1-4 minor Deaths (as per the Deck of Many Things)
Lawful-aligned souls and spirits: Wee Jas (25%), or otherwise as per above