If a caster gains enough experience to be able to use the True Polymorph spell, are they able to use it to just true Polymorph their own body into a younger version of itself? Would that work?

If not, why wouldn’t it? Would you be able to true Polymorph yourself into a different race and live longer that way? If so, this is an easy way to attain immortality that I hadn’t thought about until now. 

I don't see why that wouldn't work, but in the context of the game....why would it matter? Like, we all know elves live for hundreds of years, but the people who play elves don't often see their characters die of old age. Or, if they do, it's because of some hand-wavy time-skip campaign closer.

Since the rules don't say whether the caster's original body ages while transformed or whether the new body ages (presumably it does), it's up to the DM what sort of immortality you might achieve this way.

The Clone will let you transfer to a younger version of yourself if you ever die, and it's a lower spell level than True Polymorph. If you don't mind changing your race, Reincarnate will create a new adult body for you for even less and at a much lower level.

High-level Oath of the Ancients Paladins can't die of old age and don't suffer any drawbacks from aging, so they're effectively immortal if you don't care about looks. High-level Druids and Warlocks of The Undying age at 1/10th the normal rate, which lets long-lived races live for thousands of years before having to worry about switching to a new body.

When all else fails, no one ages in the Astral Plane. Just ask the Githyanki.

I'm going to say no due to the 1 hour limit on True Polymorph. If you concentrate on it for it's hour duration and have it stay indefinite, if it gets dispelled (Meaning anti magic fields, certain caers, another spell plague) means you are jumped right to your old age again. It is a nice temporary, albeit, fragile, form of immortality. But Clone is a much more effective spell. I'd pitch the idea to the guy who sorts out these small things (I forget his name but someone will know) but I also think that by casting it again, you'd have to break the first one, which would bring up the same issue of jumping back to your old age, I'd think.

Follow up question: RAW, could you True Polymorph somebody else into a different class? Like could a Wizard True Polymorph a Fighter into a Sorcerer?

Quote from VanZoeren >>

Follow up question: RAW, could you True Polymorph somebody else into a different class? Like could a Wizard True Polymorph a Fighter into a Sorcerer?

True Polymorph replaces your statistics with those of the creature you're transformed into. You don't use anything in your character sheet.

True Polymorph can turn someone into a sorcerer if you know of a creature that's a sorcerer and you transform them into that creature.

I might end up making a new thread because I I having other questions, but I have another follow up;

Can I True Polymorph an object into myself, effectively creating a permanent simulacrum/a clone? Making two of me run around, if i were some 20th level caster

Quote from VanZoeren >>

I might end up making a new thread because I I having other questions, but I have another follow up;

Can I True Polymorph an object into myself, effectively creating a permanent simulacrum/a clone? Making two of me run around, if i were some 20th level caster

Object into Creature. You can turn an object into any kind of creature, as long as the creature's size is no larger than the object's size and the creature's challenge rating is 9 or lower. The creature is friendly to you and your companions. It acts on each of your turns. You decide what action it takes and how it moves. The GM has the creature's statistics and resolves all of its actions and movement.

If the spell becomes permanent, you no longer control the creature. It might remain friendly to you, depending on how you have treated it.

By the time you get access to this spell you are way, way, way beyond CR 9.

Technically speaking, unless theres a RAW write up somewhere that states otherwise, player characters do not have CR ratings.

Possible loop hole - turn into a creature that is immortal like a dragon and then use its ability to "polymorph" into yourself. It isn't considered a "shapechanger" and you'd technically still be a dragon as it retains the dragon's stats and abilities.

Dragons aren't immortal - they can just live for a really long time. That's why some dragons become Dracoliches, so they don't die of old age.

Quote from Pseudoimmortal >>

I'm going to say no due to the 1 hour limit on True Polymorph. If you concentrate on it for it's hour duration and have it stay indefinite, if it gets dispelled (Meaning anti magic fields, certain caers, another spell plague) means you are jumped right to your old age again. It is a nice temporary, albeit, fragile, form of immortality. But Clone is a much more effective spell. I'd pitch the idea to the guy who sorts out these small things (I forget his name but someone will know) but I also think that by casting it again, you'd have to break the first one, which would bring up the same issue of jumping back to your old age, I'd think.

 So you could say True Polymorph would render you as some kind of Psudoimmortal 

Seems like Clone is way easier. Grow yourself a backup body that lasts indefinitely, and make sure to set aside a big diamond for your next casting. Die of old age (or accident or whatever) and bamf into your new, young body. First thing you do in your new body is start a new clone (using your stashed diamond and, say, your pinky toe) growing in the tank and lay low for 120 days. Then go off adventuring and rinse and repeat. (But remember job one is to replace your diamond to stash with the tank again for next time.)

As I did with my Wizard, cast demiplane where nobody can see you do it or ever let anyone else in. While inside, use wish to cast clone so you don't need the material components nor the time for the clone to mature and make the clone of younger age. Rinse and repeat until the end of all things. Make sure you have a spare spellbook and components in there for when you come back or it will be a bad time.

This sounds like it could lead to a pretty entertaining campaign of some kind... where some powerful wizard is causing all sorts of trouble and the party learns at some point that the wizard actually used True Polymorph to stay young, so it becomes a challenge of trying to get close enough to the wizard to dispel the polymorph so the wizard will just rapidly age to death.

Easiest way .. True Polymorph is a 9th level spell...so is Wish. Just wish yourself immortality (if your prone to living dangerously) or use it to cast Clone. When you come back you'll still have Wish memorised and can cast it again to create a new clone. Other trick is if your a human use True Polymorph to become a elf or another super-long lived race or you know just go litch :)

I have a half elf sorcerer draconic bloodline who's father according to storyline was a Gold Dragon in human form. My character's father was killed on his way to a council of worms at a place called Dragonstone shortly after my birth. My mother was assassinated 8 years later by the same group that killed my father. Since the draconic bloodline is so close to me genetically; I was wondering if whenever I go to use a spell like alter self or polymorph would I have a little more latitude because of my father's natural ability to polymorph at will?

Quote from Wraith0415 >>

I have a half elf sorcerer draconic bloodline who's father according to storyline was a Gold Dragon in human form. My character's father was killed on his way to a council of worms at a place called Dragonstone shortly after my birth. My mother was assassinated 8 years later by the same group that killed my father. Since the draconic bloodline is so close to me genetically; I was wondering if whenever I go to use a spell like alter self or polymorph would I have a little more latitude because of my father's natural ability to polymorph at will?

 
Rules-as-Written: No.

Rules-as-Fun: check with your DM.

I really do not know how this could work out.