|The Astral Plane is a plane of spirit and energy. It is completely unlike the planes of men. The wizard (or other spell user) journeys there in spirit form (raw animus). Only the caster's spirit goes, all of his or her material possessions remain on the planes of men with his or her body.
On the Astral Plane the caster's spirit is attached to his material body by what appears to be an umbilical cord of a silvery colour (thus called the Silver Cord). This cord is not in fact unique to the Astral Plane, the silver cord is an extension of the network that attaches or anchors animus to the body. If a wizard were to use the spell Anima Travel, to travel in spirit form in the planes of men, the silver cord would still connect the caster's animus to his or her body. This silver cord is the life link. If it is cut, or severed, the owner of the silver cord has some severe problems. Certain spirit and demonic creatures may damage or sever the silver cord as may some magic artifacts and certain spells. If the silver cord is damaged, the caster should return to his or her body for 24 hours to let the silver cord 'repair/restore itself.'
The Astral Plane itself is rather disconcerting to the novice visitor. There is no 'ground' on the Astral Plane, nor is there an up or down. It is just a vast space, apparently without gravity (but since everything is spirit there, how can one tell?). The Astral Plane appears to be filled with a glowing multicoloured vapor or mist. There are large brightly coloured regions of mist of all imaginable colours; there are even a few colour empty regions, simply white. Because of this 'mist' visibility is not far and orientation in the Astral Plane is hard. Generally, one needs some form of spell or device to provide directions.
What purpose does the Astral Plane serve? It is not completely clear to most scholars, but apparently, the Astral Plane is a nether ground, or highway, between the planes of existence. Only spirits may traverse it, and most religions believe that the spirits of the dead must cross it to reach the home planes of their various deities.
What is known is that various creatures, many of which are of malevolent natures, roam the Astral Plane. It is well known to wizards that demons frequent this plane. It is in fact on the Astral Plane where wizards find new demons that have never been bound before. What these demons are doing there is not clear, but they often wander freely on the plane. Spirits of the dead and all sorts of other spirits traveling between the planes of men and the planes of gods also travel there.
In principle, deities may also wander this plane, but none has ever been recognized, or at least categorically recognized by any wizards. Clerics and priests will make all sorts of claims, but their views are typically biased by their religious fervor.
On the Astral Plane, spells that require material components will not work, unless the spell is specifically designed to use material components on the planes of men and effect the Astral Plane. Further spells that rely on physical effects to produce damage have no effect on the Astral Plane, since there is nothing physical to effect. Energy based spells, such as lightning and fire based spells, do work, but they do significantly less damage than on the Planes of Man. Only pure energy spells or spells oriented towards spirits will do actual damage. Spells of an indirect nature, that do not rely on physical effects, nor do direct physical damage, work normally.
If one knows where one is on the Astral Plane, relative to the Planes of Man, then in principle it is possible to effect the Planes of Man with some spells from the Astral Plane. The difficulty lies in having a clue as to the correspondences, and getting any information about what is happening on the planes of men.
The only wizard spell to really provide such information is my own mentor’s: Aerelion's Astral Seeker. The Seeker will seek out an individual on the Planes of Man, from the Astral Plane. This spell will allow the caster to attack the target's animus on the planes of men from the Astral Plane.
If the silver cord is severed while on the Astral Plane, the spirit is basically stuck there. Unless the caster has some means, spell or otherwise to form a new body on the Planes of Man, or receives help from another, he or she is stuck for eternity. On the Astral Plane, animus will not dissipate, unlike on the Planes of Man, however this only means the individual is stuck there until the end of time. His or her body on the Planes of Man will die within a few days, depending on the strength of the individual’s own Animus.
Of course, at such a point one is basically dead; in theory, if one’s religious contracts are in order, it should be possible to somehow get to one’s reserved afterlife in the Plane of one’s particular deity or pantheon. However, exactly how that works, or how one locates said plane is beyond not only the scope of this text, but also the purview of Wizardry. Please check with one’s preferred priest or cleric for more information.
In any event, this severing on the Astral Plan may or may not be preferable to having one's silver cord severed while traveling from one's body on the Planes of Man. When this occurs, the spirit is in real trouble and will immediately need to find some means of protecting itself or it will be dissipated back into nature. The body will die in the same time period. A spirit whose Animus dissipates into nature, cannot be reincarnated or raised, or resurrected by normal means. Only extremely powerful cleric invocations can bring the individual back.
An individual, whose spirit is trapped on the Astral Plane, can usually be contacted, by the appropriate, speak/commune with dead/spirit type spells. Which brings up an unpleasant point for most self-respecting wizards. If one is in one of these situations, often times the person best suited to help the individual is a highly experienced necromancer. Of course, such help may be worse than no help; but necromancers specialize in securing spirits on the Planes of Man. Naturally, there would be a steep price, in many ways, for dealing with such an individual. Slavery to the necromancer as an undead creature, being only one possibility.