Time ravage states:
If the save fails, the target also ages to the point where it has only 30 days left before it dies of old age.
How does this spell interact with true polymorph? If you are polymorphed into another creature, then fall victim to time ravage, will reverting to your normal form prevent you from dying to time ravage?
This may depend on how you rule natural aging for true polymorph, here is mine:
From here, it seems reasonable enough to say that you age according to the new creature's aging, since you are the new creature. Further, since aging is generally the result of physical processes, it seems reasonable to say that the original form does not age because it does not exist while you are polymorphed. All the processes, the exposure, that leads to the effects of aging is not happening to your original form, while it is happening to your polymorph form.
If your answer depends on a particular ruling for natural aging, please include it.
Best Answer
Time Ravage effects carry on even if one reverts back to its original form.
The Time Ravage description says (emphasis mine):
Hence, we have a precise condition for ending this spell, which does not depend on aging rules adopted at one's table: even assuming that the original form does not age while under the effect of True Polymorph, as quoted in the question, Time Ravage effects still hold on a target that decide to revert back to his original form.
There is still some debate about carrying spells' effects on polymorphed creatures (see, for example, this Q&A), but the description of Time Ravage is quite clear: the sole conditions to end this spell consist in using Wish or Greater Restoration (the latter cast with a 9th level slot).