Can you effectively achieve immortality with Magic Jar?

[Dalebert]

Albeit tediously. My thought is, could you just keep recasting to extend the duration after your body is gone? Could you potentially get a healthy (soulless) body to inhabit that you could just stay in without resistance?

[snailgosh]

I'm pretty sure you can only inhabit bodies with souls, effectively replacing the original soul.
From the RAW I'd say recasting the spell sends your soul back to the gem.
But you should be able to switch back between gem and host body without access to your original body.
You'd automatically die when dispelled, though. And propably upon entering an AMF as well.

[Waker]

Arguably the best kind of body to inhabit would be an undead. The majority of which already lack a soul, so they wouldn't hold a specific grudge even if the spell should end and of course you would have access to all the benefits of undead, like not needing sleep/food/etc. As for you body you could probably just use Shrink Item, since it is technically a dead body. As for what happens if you die and return to your body, I'm not sure if you would simply cancel the spell since your living body would no longer be a valid target or if you would just be put in some kind of stasis until the spell ends.

[snailgosh]

Yeah I think the safest way would be to have a strong, resilient mindless undead under your control that you order to fail will saves against you. If you're confident in the bodies' sturdyness you can have it swallow the soul gem.

Doesn't help against dispelling and AMFs though.

[Daishain]

Not strictly RAW as far as 3.5 is concerned, but 5E's version of the Imprisonment spell could solve your main problem.

It lets you specify conditions to end the spell.

So, cast Magic Jar, possess something, and then cast Imprisonment on your body, with the condition that if your soul returns to it, the spell ends.

As a result, your body is extremely well protected, and is in stasis, while you are free to act through others. If you walk into an AMF, or get hit with a strong dispel, you don't die, you just wake up wherever you hid your body and are free to repeat the process. Might have a few kinks to work out of the joints though.

This wouldn't be true immortality. But living like that for a few million years would not be out of the question.

[sleepyphoenixx]

Not strictly RAW as far as 3.5 is concerned, but 5E's version of the Imprisonment spell could solve your main problem.

It lets you specify conditions to end the spell.

So, cast Magic Jar, possess something, and then cast Imprisonment on your body, with the condition that if your soul returns to it, the spell ends.

As a result, your body is extremely well protected, and is in stasis, while you are free to act through others. If you walk into an AMF, or get hit with a strong dispel, you don't die, you just wake up wherever you hid your body and are free to repeat the process. Might have a few kinks to work out of the joints though.

This wouldn't be true immortality. But living like that for a few million years would not be out of the question.

Your body needs to be in range when the spell ends (or you die). So Imprisonment won't work.

[Dalebert]

I guess there's no way to make an empty body to occupy permanently unless it's "owned" by you. What comes to mind is using the spell to magic jar someone so you can kill your old body and cast reincarnate. Then you have a fresh young body that's tied to your soul. So when you end the spell, and stay within range, you will return to your reincarnated body.

[Jack_Simth]

Albeit tediously. My thought is, could you just keep recasting to extend the duration after your body is gone? Could you potentially get a healthy (soulless) body to inhabit that you could just stay in without resistance?

The general method... with an array for tracking:
Y: Your Body
(y): Your soul
T: Your Target Body
(t): The soul of your Target Body (which gets destroyed)
P: Your Patsy's body
(p): Your Patsy's Soul.
J1: The first Jar
J2: The second Jar.

Starting condition:Y(y), T(t), P(p), J1, J2
1) Cast Magic Jar: Y, T(t), P(p), J1(y), J2
2) Posess target: Y, T(y), P(p), J1(t), J2
3) Use the soul in the gem as an optional component for a spell (see Book of Vile Darkness) to eliminate it forever (caused problems with two souls in one body otherwise: Y, T(y), P(p), J1, J2. Possibly do so to cast the spell in step 4.
4) Cast another Magic Jar: Y, T, P(p), J1, J2(y)
5) Posess a patsy: Y, T, P(y), J1, J2(p)
6) Dispel the Magic Jar from 1: Y, T, P(y), J1, J2(p) (doesn't change anything)
7) Dispel the Magic Jar from 4: Y, T(y), P(p), J1, J2

So yes, if you don't mind destroying souls every so often, you can usurp a body with the help of a minion - and because no magic is left after, a Dispel or an AMF doesn't affect anything when you're done.

Of course, if something kills the body you're in, well, you stay dead.

[Dalebert]

Jack, let me know if I understand this correctly. You seem to be basing this strategy on the idea that when the spell says "your body" it means whichever body you were occupying when you cast the spell (even if it's someone else's body). I'm not sure that can be assumed. I am inclined to interpret "your body" as your original body and not the body you just happened to be in when you cast the spell, though I would like to be wrong about that.

[sleepyphoenixx]

There's an amulet that effectively grants permanent Magic Jar here (http://www.wizards.com/dnd/files/MagicItems.pdf).
It doesn't solve the main issue (dispellable and affected by AMF) though so it's not really a reliable method to achieve immortality.

I suggest taking a look at the Guide to Immortality (http://www.minmaxboards.com/index.php?topic=1179). Pretty much anyone can use at least one method here to become immortal.
If nothing else you can always buy a power stone of True Mind Switch, invest one cross-class rank into Use Psionic Device and buy a few buffs like Surge of Fortune, Greater Heroism, Eagles Splendor etc. to hit the DC. You only have to do it once every few decades after all.

[Jack_Simth]

Jack, let me know if I understand this correctly. You seem to be basing this strategy on the idea that when the spell says "your body" it means whichever body you were occupying when you cast the spell (even if it's someone else's body). I'm not sure that can be assumed. I am inclined to interpret "your body" as your original body and not the body you just happened to be in when you cast the spell, though I would like to be wrong about that.
Hadn't thought in that direction, but yes, that is one of the underlying assumptions. It's not directly addressed one way or the other, and falls under the "ask your DM" segment.