@JeremyECrawford went back and re-listened to the polymorph Sage Advice and I have a follow up question: once a true polymorph spell is made permanent from concentrating for the full duration, does reducing that creature to 0hp still cause them to revert to their original form?
— Eugenio Vargas (@eugenio_vargas) January 2, 2018
Is one way to read it. Another, and one that I found a tweet from @mikemearls backing, is that once it’s permanent, it’s PERMANENT and magical intervention is required even if the creature is reduced to 0hp.
— Eugenio Vargas (@eugenio_vargas) January 3, 2018
The text of the spell says it has no effect on a creature with 0 hit points. That statement is made after the bit about lasting until dispelled. At 0 hit points? The transformation ends.
— Jeremy Crawford (@JeremyECrawford) January 3, 2018
Wait, so that means you can get out of a true polymorph spell just by taking enough damage? That makes it a lot weaker.
“Get out of” almost certainly means dying unless something else heals you. And the creature would have to have knowledge about the spell and suicide. And if it’s an object, suiciding would be hard. No, that’s a powerful spell