What happens if someone cast Magic Jar (PH p.250) on a person who has been revived by a Revenance spell (Spell Compendium p.175)? Does it keep him alive after Revenance has ended? Does the caster of Magic Jar die in his place? Do they both live? Do they both die? Also, what happens if the person revived by Revenance casts Magic Jar?
Q. What happens if a caster casts the spell spell magic jar [necro] (PH 250-1) and uses magic jar's effect to possess the body of a creature brought back from the dead by the spell revenance [conj] (SpC 175)?
A. The caster of the spell magic jar--assuming a failed saving throw on the part of the ally who was the target of the the spell revenance--possesses the body as per the spell magic jar until the duration of the spell revenance expires. The spell magic jar says that
Attempting to possess a body is a full-round action. [...] You possess the body and force the creature’s soul into the magic jar unless the subject succeeds on a Will save. Failure to take over the host leaves your life force in the magic jar, and the target automatically succeeds on further saving throws if you attempt to possess its body again. If you are successful, your life force occupies the host body, and the host’s life force is imprisoned in the magic jar.
Q. Does the spell magic jar keep alive the body brought back from the dead by the spell revenance after the spell revenance expires?
A. No. When the spell revenance expires, the ally on whom it was cast dies, and that ally was the creature when the spell was cast--body and soul. The spell revenance says that the the ally "dies as soon as the spell [revenance] ends." The spell revenance "functions as if raise dead (PH 268) spell had been cast upon" the ally, and that spell mandates a body, as does the Target entry of the spell revenance.
Q. If the ally possessed by the caster of the spell magic jar dies when the spell revenance expires, does the caster of the spell magic jar also die?
A. Yes, if the caster of the spell magic jar is out of range of the receptacle used as the spell's focus. No, if the caster's within range of the receptacle used as the spell's focus. The spell magic jar says
If the host body is slain, [the caster] returns to the magic jar, if within range, and the life force [i.e. soul] of the host departs (it is dead). If the host body is slain beyond the range of the spell, both you and the host die. Any life force with nowhere to go is treated as slain.
I'm not sure what to make of the phrase treated as slain, except that it's only treated as so inventive DMs can create plots using jarred souls. It's probably wiser, instead, to house rule the text to say just slain rather than the text's treated as slain (but not really be slain, mind you), if only to avoid potential confusion and hard feelings.
Q. What happens if the ally brought back from the dead by the spell revenance uses the effect of the spell magic jar to possess another creature?
A. Until the spell revenance expires, the spell magic jar can be used as descrbed. Once the spell revenance expires, the ally--even if its soul is located in another body or the spell magic jar's focus--dies. Although "[d]eath causes the character's soul to leave the body" it also causes the soul to "journey to an Outer Plane" (PH 307). So while its arguable that the soul has already left its original body--therefore satisfying the first part of the dead condition already--, this second part of the dead condition's description of the soul's fate can't be prevented by the spell magic jar, and off goes the soul to its reward.
The solution is all in the text of magic jar once we consider that revenance kills his target.
If the host body is slain, you return to the magic jar, if within range, and the life force of the host departs (it is dead).
When revenance ends, provided the host body is still in range of the jar, the revived character dies and the caster's soul gets back into the jar. If the jar is out of range...
If the host body is slain beyond the range of the spell, both you and the host die.
...which happens to be pretty self-explanatory.
So no, there's no way to keep the revenanced character (or even his body) alive.
If the caster is the target of the revenance spell himself, his soul gets into the jar and then two things might happen, depending on interpretation.
- When revenance ends, it kills the body and the soul of its target. If the soul was in the gem, it just ceases to exist. If not, the solu trapped in the gem tries to get back to its body and might die as well if the range is too high.
- When revenance ends, the body is slain. The soul is safe inside the gem and can still do things and possess people. When the spell ends, there's no more alive bodies to get back in and the caster dies.
I personally favor the first one: when somebody dies, it's his soul departing from its body and going to the appropriate planes (depending on the setting).