In my recent post about the spells in B/X D&D, Magic Jar was listed as being particularly confused and confusing. I've since arrived at what I think is a rather simple solution for just about all its problems. Furthermore that solution requires none of the even more complicated AD&D machinery. I actually quite like the resulting spell, but your mileage may obviously vary! Let's start with the original spell itself, straight from the B/X Expert rules (in all probability "fair use" applies):
With this spell, the caster puts his or her body in a trance and transfers his or her life-force to an inanimate object (magic jar) within range. From this object, the spell caster may attempt to possess (take over) any one creature within 120' of the magic jar. If the victim makes a successful saving throw, the possession has failed and the caster may not try that victim again for one game turn. If the victim fails the saving throw, the creature is possessed and its body will do as the caster wills. While under the control of the spell caster no spells of the possessed may be used. If the possessed body is destroyed, the magic-user or elf must return to the magic jar. From there the caster may try to possess another body or return to his or her own. The caster can be forced out of the possessed body by a dispel evil spell.
Destroying the magic jar while the caster's life force is in it kills the caster. Destroying the magic jar while the caster's life-force is in another body strands the life-force in the possessed body. Killing the caster's real body strands the life-force in the magic jar until the caster can possess another body! Once the caster returns to his or her real body the spell is over.
The first complaint I had was about the two ranges used by the spell. I now think that those are fine provided we interpret them as follows: The caster's body has to be close to the magic jar to initially transfer the life-force. Once in the magic jar, the caster has completed "the hard part" and now has a somewhat larger range to find victims in. However, any "soul traffic" between victims and the magic jar must happen in that 120' radius. Finally, the "traffic" between the jar and the caster's body must happen in that 30' radius, including on the "way back" at the end of the spell.
This solves two more questions I had: What range counts for returning to the jar, the 30' or the 120'? What happens when a Dispel Evil pushes the caster out and the magic jar is too far away? It also solves a question I didn't explicitly pose, but one that's implicit in the spell as written: What happens if the possessed body dies and the magic jar is too far away? With the "strict ranges" interpretation, both of these result in the casters immediate demise. Neat!
But I had a lot more questions. Turns out that most of these become equally easy to answer when we add the following to the spell description (paraphrased):
The victim's life-force gets sucked into the magic jar while the caster has possession of the victim's body.
Let's see what this solves. Can the caster "chat" with the victim? No. Does the victim remember anything the caster made his possessed body do? No. Does the caster gain any of the victim's knowledge, spells, skills, etc.? No. Can the victim attempt to "push out" the caster's life-force, maybe similar to what Charm Person allows? No. See how easy that is? No need to write several unsatisfying paragraphs (and a custom "add wisdom and intelligence of victim and caster, then compare on this really complicated table" rule) like AD&D did.
It also solves a related, although mostly metaphysical problem: If the victim's life-force doesn't go into the jar, we now have two "souls" in one body. Can that be? Wouldn't the universe implode? (Don't complain, I said it was a metaphysical problem, didn't I? Actually there's a deeper one too, namely "Do souls that hop around bodies exist at all?" but let's not go there.)
Maybe least obvious is that our little addition explains (indirectly) why the caster should be allowed to make use of his or her spells while in the victim's body. (Always assuming that the body is capable of performing the necessary verbal and somatic activities those spells necessitate.) If what we're dealing with is essentially a "soul swap" that includes whatever is "stored in the brain," well, then the memorized spells of the caster should go with him. Just like the victim's spells (if any) go into the jar together with the victim's life-force and are hence not available to the caster. While the caster (or the victim) is in the jar, though, spells cannot be cast because there's no way to perform those verbal and somatic elements. And while the B/X version doesn't mention the caster using spells in the victim's body, AD&D clearly allows it. So there's predecent.
That leaves only one of my original questions, namely whether the caster can leave the victim's body and return to the magic jar voluntarily. I think that has to be a resounding "Yes!" because if it's possible for the caster to get stuck in a beetle by accident, well, presumably that's not where our hero wanted to end up, is it? If he or she now had to commit "beetle suicide" as the only way out, that's just too depressing.
But I have two twists left, at least one of which I hope you'll appreciate (I try so hard to write pleasing D&D posts).
First it seems pretty sad that the victim of Magic Jar can do nothing but sit in the magic jar until the caster decides to return. Imagine the victim's body (and the caster's life-force with it) dying miles away: The "poor soul" would be in the magic jar forever. Literally. (Unless someone casts Dispel Evil on the jar by accident, of course killing the victim in the process.) How do we solve this?
Let's add a chance that the victim can take over the caster's body!
Where do we take it from? Charm Person of course! After all a "smart soul" should be able to figure out what's going on much more quickly than a "dull soul," right? (A scary alternative would be to allow the victim to use the magic jar just like the caster did. Think it through, hilarity would ensue for sure as entire cities start swapping bodies and souls.)
Twist number two is only applicable if you import certain BECMI spells into your B/X game like I tend to do: A cleric can use Speak with the Dead to communicate with the life-force trapped in the magic jar. Why? Well, it's a "disembodied soul," right? Potentially the "disembodied soul" of someone who is actually dead as well. Seems perfectly sensible to me! And in terms of the game it also gives players a way to communicate with that evil wizard in the magic jar to maybe negotiate some kind of deal. More options are always better!
Alright, that was a lot of talking. I now give you my version of Magic Jar written up in B/X style (well, as much as I am able to copy that style anyway):
The caster puts their body in a trance and transfers their life-force into an inanimate object within 30'. From this magic jar, the caster may once per round attempt to possess any creature within 120'. If the victim saves against spells, the possession has failed and the caster must wait one turn before trying that creature again.
If the victim fails to save, the victim's life-force is transferred to the magic jar as the caster's life-force takes control of the victim's body. The caster's life-force can return to the magic jar (and thus reverse the process) only if the magic jar is within 120' of the victim's body. This applies whether the caster leaves voluntarily, is forced out because the victim's body is killed, or is forced out by a Dispel Evil spell. If the caster's life-force cannot return, it perishes. While in the victim's body, the caster may use any memorized spell as long as the body is in principle capable of spell-casting.
While in the magic jar, the victim's life-force gets another save against spells as per Charm Person: Intelligence 13-18 once per day, 9-12 once per week, 3-8 once per month. If successful, the victim's life-force can take over the caster's body. Destroying the magic jar kills any life-force within it and possibly strands the caster's life-force in the possessed body. Killing the caster's body prevents any life-force from returning to it. Once a life-force returns to the caster's body from within 30', the spell ends.
Okay, so it's a little longer than the original, but I think it's worth it. Let me know what you think of the new version! And maybe someone even notices the one thing I totally left open to interpretation despite it being addressed in the AD&D version of the spell. Anyone?
Update 2015/10/19: There's one big tradeoff I forgot to discuss, sorry. Allowing the caster to cast further spells in the victim's body means that he or she could cast Magic Jar again! Visualize this as a "trail of bodies and magic jars" if you wish.
I didn't want to add a restriction of the "any spell except another Magic Jar" kind because that seems petty. On the other hand, repeated casting of the spell requires that we fix which body counts as the original. The simplest story is probably to just use the body the caster was in for a certain Magic Jar as the original for that spell. So the caster could return from the second victim to the body of the first victim for example, thereby ending the second Magic Jar spell.
This works for the most part, except if the truly insane is attempted: The second (or tenth, or onehundredfortyseventh) Magic Jar is used to "possess" the original caster of the first Magic Jar again. (In other words, the caster is trying to "imprison" a whole bunch of people in magic jars and come out "on top" by possessing himself again.) Two things help to avoid that:
First, note that I didn't specify whether the caster can memorize spells while in a victim's body. True, the way I interpreted the rest I guess it would be natural to allow it, however that would mean that no upper bound on the length of the "chain of jars" exists, a spooky proposition. So the concerned DM could certainly use that to keep things "managable" as it were.
Second, note that the original body of the first Magic Jar does not contain a life-force. Since we described the process of possession as an "exchange" of life-forces, the concerned DM could rule that the original body cannot be possessed again: it lacks a life-force to imprison in turn.
And if all of this sounds like a huge hassle to you, the line "The caster's life-force can only participate in one Magic Jar spell at a time." would also fix everything. (At least if we ignore that the caster of one Magic Jar could be the victim of someone else's Magic Jar as well. Dicey!)
All three options work for me. Now I wonder if I should I rewrite the spell for this or just leave it as commentary? Hmmm...