Age Effects

[thereaper]

What effects can affect a character's age?

I'm especially interested to know of effects that can de-age a character.

What I know of so far:

Ghost (can age and potentially even kill a character)
Potion of Longevity (can de-age a character at first, but subsequent uses are increasingly likely to age the character instead)
Wish (likely to have unpleasant side effects)
Reincarnate (unpleasant side effect of changing race)
Clone

[Composer99]

There's a wild surge effect (from wild magic sorcerer) that changes your age.

[Goldlizard]

The lair effects of a Sphinx

[MoiMagnus]

A lot of problems with de-aging effects is the lack of definition of "dying from old age". What the heck does that mean? Do souls expire at some point, so that you still die from old age when your body is in perfect condition and you are immune to diseases? Is it the fact of dying peacefully that makes you unwilling to come back to life by default?

+ Transmutation wizard have can de-age peoples, but without changing their lifespan (which is weird, because that mean you will die from old age in the body of a 20 yo person), so it might not count for you.
+ Raise dead (or the restore life effect from the transmutation wizard) does not have an exception for old age, so you can just use that repeatedly. Assuming you don't start dying from old age every minutes but that it is more every month or year.
+ True Polymorphism might allow you to chose a younger version of yourself, though it depends on your DM. It is also unclear what happen when you polymorph into a race with different lifespan. (Warning: True Polymorph can be dispelled, which would probably kill you if you used it for de-aging yourself. Or maybe your back at your age when casting it? Depends on your DM).

[gloryblaze]

The 9th level spell Time Ravage from EGtW, on a failed save, ages the target "to the point where it has only 30 days left before it dies of old age. In this aged state, the target has disadvantage on attack rolls, ability checks, and saving throws, and its walking speed is halved. Only the Wish spell or Greater Restoration cast with a 9th-level spell slot can end these effects and restore the target to its previous age."

[Nagog]

Do you specifically want de-aging? Because some examples (the Ghost in particular) only age you forwards. If your open to either, there's a 9th level Dunamancy spell that ages somebody to 30 days before their death.

[thereaper]

I was interested in both, but I'm especially curious about reversing age because of the permanent aging effects. I want to know if there are practical ways of negating the effects of, say, a horrifying visage.