Magic jar is the best 6th level spell in the game, and I doubt anyone can convince me otherwise. Even magic jarring a lower end CR creature adds so much survivability to us, as well as possible damage output, that there’s no reason not to use it (unless you’re some a lawful goody-two-shoes who doesn’t believe in stealing other peoples bodies). There’s issues with this process, the two biggest things holding magic jar back is our inability to jar into non-humanoids, meaning we struggle to choose our targets until we can use simulacrum and true polymorph, and that the effect can be dispelled.

a quick note on magic jar: we add our hit dice to the creature we jar, because we gain their hp and retain all of our class features, one of those being our hitpoints. Magic jar also lets us retain our class features and our spellcasting.

Double Jar

So, I recently experimented with the concept of “double jar” [Shoutout to “The Pi Guy” for finding double jar!]. Double jar possesses our humanoid of choice, then casts magic jar again to possess another humanoid, from the 2nd humanoid, we smash the jar, being forced back into our previous body, aka the body of the first thing we jarred. We are now and forever the inhabitant of the body we jarred first, unless we make the choice to use magic jar again or die. We can even clone ourselves in this state.

Nystul + Jar

So, we can solve the dispelability issue of magic jar. Can we find more suitable targets earlier? Actually, we can! Nystuls turns out to allow us to designate another creature as a ‘humanoid’. So, we can take our elemental of choice from the ‘conjure elemental’ spell, planar bind it, nystuls it into a humanoid, and possess it. [We might take a trip to whatever plane of existence the elemental lived on if we lose planar binding, so, make an effort not to, but by my reading we are ‘us’ when possessing a body, and are native to the material plane for banishment or other effects funny enough, we need to nystul back into something that can be planar bound. I’d suggest then nystuling again into an ooze so an enemy can’t wishbind you, but that’s paranoid wizard to an extreme degree]. I suggest an invisible stalker for your elemental. 50ft hover speed, medium sized, a ton of condition immunities including exhaustion, and we’re invisible innately. We also gain poison immunity, and nonmagical BPS resist. Finally we get a +10 to stealth. with pass without trace up this gives us a lowest possible roll of 21.

Putting it together

Double Jar and Nystul Jar put together gives us fantastic versatility in what we choose to jar as well as making us permanently inside our body of choice, barring dying or casting magic jar again. This means at wizard level 11, we can replace our race with an invisible stalker (or other elemental of choice) as long as we keep the binding up if we are sent back to the elemental plane on the condition of losing it, or, if we are native to our own plane, simply get rid of planar binding. In the case that it is ruled that we are sent back to the elemental plane, I would instead of trying to keep planar binding forever, learn teleportation circle before we get magic jar, allowing us to cast it and come back to the material plane. This requires a small amount of free time in the dimension, which we could get by simply casting rope trick. we could also eventually learn plane shift to just harmlessly be sent into the plane, then shift out in an action. Plane shift requires us to be at least level 13. This might mean we have access to someone with “conjure celestial” which, could also supply us with an amazing body to jar into, but that’s a story for another time.

With both of these techs in play, we have a huge selection of creatures we can be, and, once our choice is made, it can’t be unmade. This gives us a ton more survivability as well as the option to do normal attacks.

Going even further beyond

So, nystuled double jar is already amazing (and already pretty likely to break the game), but can we go further? It’s possible, but unlikely. The question hinges on how much hp does our catatonic corpse have? If it copies our health before we left it, then, it’s possible we can use this to generate infinite health. The process is a bit complicated, so here are the steps:

1. magic jar a barbarian for the juicy health pool
2. Chronurgist (for conveinince, any 2 wizards could work, but chron works best) buddy magic jars my “catatonic state” body, gaining my previous HP along with his own
3. I magic jar my chronurgist buddies body, gaining his previous HP along with my own
4. Useless barbarian corpse is disposed of, get new barbarian
5. Chron Fren in my body possess new barbarian, leaving catatonic body of his own with presumably the same HP it had when he left
6. Me, now in chron frens body, magic jars what used to be my body, gaining my old HP, chron’s HP, and my HP again.
7. Chron fren magic jars into what was his body, now my body, with his hp, my hp, and his hp again
8. dispose of 2nd barbarian

Repeat cycle until sufficient health numbers have been reached.

unlike double jar, which is rather clear in comparison, infinite jar relies on assigned hp numbers to catatonic state bodies left by the spell itself, which, is really dubious. It also relies on that being equal to the person in the body before it left, and not based on some other qualifier. There’s also no soul in the body to put in the jar, so it’s possible it’d just fail.

dubious RAW and almost for sure table banned RAI, infinite jar tech is unlikely to see real play unless you have an ultra-generous DM, and it means losing out on the benefits of magic jar besides health. Infinite health is still amazing if you can get a hold of it though, but I doubt i’ll be making much use of it.