On one hand: good that it's been nerfed to not be stupid mechanically.

On the other hand: the theme of the spell is kind of broken by your specie being kept, as is your size. Wow, you magic jarred into a large humanoid. Congrats, you'll now be... medium sized and be able to use breath weapons because you're a dragonborn, or small sized and be able to hide better because you're an halfling.

I like this spell from a DM's storytelling perspective. Imagine you're exploring a dungeon, then you trigger a trap and get stuck in a jar!

Possessed. Tarrasqe.

Quote from Iron_Sir_Levi >>

Possessed. Tarrasqe.

 Humanoid body/target only. It’s in the first paragraph. 

your body falls into a catatonic state

What are the EXACT stats of your catatonic body? 

"Catatonic state" is not a defined condition unless we are supposed to equate it to "can't move or take reactions."  Medically, there are so many different kinds of catatonic state.  In some you move, in some you don't.  In some you speak, in some you don't.  Is this just GM fiat or is something specific intended?

If I had to guess, it does sound like maybe it's "can't move, can't take reactions, and only Action you can take is (as written)" but that means you can speak, can do all the things that are not Actions except move or take reactions.  When you speak, it comes from your catatonic body's mouth.  The container is all input, your body is still all of the output.

Another clarification provided is that it is still considered "living."  I'm assuming that means needs air to breathe if you always needed air, needs food/water " "(intubation?), ages, grows hair/nails, and other *ahem* bodily functions.  What about atrophy/hygiene?

You otherwise keep your game statistics.

After possession, when you gain any class features or ASIs through levels (assuming you do gain levels in the controlled body and that "keep" does not equate to "keep at the time of possession", right?), does both your catatonic living body and your controlled body gain the feature/stats?  Imagine that a leveled feature read something like "upon reaching X level, you immediately shape-shift into..." Would such a feature affect both bodies?

Is your original body targetable?  If yes, by your own controlled body and others?  Similar question as above - if you can target yourself, do both bodies get affected?  If you target "self" or are otherwise self-targeted while in the controlled body, do both bodies get affected?

Protecting your catatonic living body seems paramount to avoiding certain and immediate death.  All someone has to do is send/teleport/move your original body 100ft away from your controlled body for even a millisecond, including just sending it to another plane/dimension.  Or vice-versa - sending/teleporting/moving you away from the original body even for a millisecond.

It's also incredibly easy to dispel - anyone capable of casting dispel magic within 120 ft of your original body, your controlled body, OR the contrainer just needs to shout "hey i think magic jar is going on somewhere near here, dispel that plz" and it is done.

So all of this is to say  - how do you BEST protect/maintain your original body's AND keep yourselves in proximity with each other AND avoid dispel magic?

Quote from SylvestreShaw >>

your body falls into a catatonic state

What are the EXACT stats of your catatonic body? 

"Catatonic state" is not a defined condition unless we are supposed to equate it to "can't move or take reactions."  Medically, there are so many different kinds of catatonic state.  In some you move, in some you don't.  In some you speak, in some you don't.  Is this just GM fiat or is something specific intended?

If I had to guess, it does sound like maybe it's "can't move, can't take reactions, and only Action you can take is (as written)" but that means you can speak, can do all the things that are not Actions except move or take reactions.  When you speak, it comes from your catatonic body's mouth.  The container is all input, your body is still all of the output.

Another clarification provided is that it is still considered "living."  I'm assuming that means needs air to breathe if you always needed air, needs food/water " "(intubation?), ages, grows hair/nails, and other *ahem* bodily functions.  What about atrophy/hygiene?

You otherwise keep your game statistics.

After possession, when you gain any class features or ASIs through levels (assuming you do gain levels in the controlled body and that "keep" does not equate to "keep at the time of possession", right?), does both your catatonic living body and your controlled body gain the feature/stats?  Imagine that a leveled feature read something like "upon reaching X level, you immediately shape-shift into..." Would such a feature affect both bodies?

Is your original body targetable?  If yes, by your own controlled body and others?  Similar question as above - if you can target yourself, do both bodies get affected?  If you target "self" or are otherwise self-targeted while in the controlled body, do both bodies get affected?

Protecting your catatonic living body seems paramount to avoiding certain and immediate death.  All someone has to do is send/teleport/move your original body 100ft away from your controlled body for even a millisecond, including just sending it to another plane/dimension.  Or vice-versa - sending/teleporting/moving you away from the original body even for a millisecond.

It's also incredibly easy to dispel - anyone capable of casting dispel magic within 120 ft of your original body, your controlled body, OR the contrainer just needs to shout "hey i think magic jar is going on somewhere near here, dispel that plz" and it is done.

So all of this is to say  - how do you BEST protect/maintain your original body's AND keep yourselves in proximity with each other AND avoid dispel magic?

If your character can cast Imprisonment or presumably have someone cast it for them, you could use that spell on the original catatonic body, choosing the Minimus Containment option and then carry it around with the freeing-from-the-spell condition that the current occupied body dies or the Magic Jar spell ends.

Edit: fixed syntax and an accidental leftover word was removed for clarity.

Quote from JustinTotino >>

Quote from Iron_Sir_Levi >>

Possessed. Tarrasqe.

 Humanoid body/target only. It’s in the first paragraph. 

 Except that they changed Nystul's Magic Aura so that it explicitly (RAW) allows masking of creature types for spells like Magic Jar (in the previous version it wasn't clear if you could, and more implied that you couldn't, but some argued that you could). Some argued that you could True Polymorph something into a humanoid and then Magic Jar them and could keep the possession after the true poly fell off, though that's firmly in "the rules don't say I can't" camp, rather than Rules as Written. 

For the new Nystul's they do have to be 'willing' though, so it does require some complicated Dominate Monster-->Nystul's Magic Aura-->Magic Jar... but yes you can possess a Tarrasqe, rules as written. 

When I control it, I keep my stats, do I also keep my abilities? Or do I get the abilities , armor class, etc of the possessed creature ? 

for example, if I’m a wizard and I possess a fighter, do I get to make use of the fighters multi attack ?

Thanks! This is exactly what I was looking for as far as protection for the catatonic body.  It doesn't directly address the magic jar itself but if you're requiring Level 9 spells to get this done (Imprisonment) then you can probably also True Polymorph that object (concentrate for an hour) and then Imprisonment the creature after an hour.  You have to kiss the ass of that creature for an hour though and hope it stays friendly.

Shame it got nerfed so hard. My table will keep using the 2014 version.

Bruh, not even saving throws, and humanoids always have shit physical stats.

Just let us take all stats except mind but without any actions and leg res.